Sudden rough idle & Hesitations after parked overnight!

[Beachdrifter]

Hi all,

I seem to be posting a lot lately, as I am getting gremlins recently.

So here is the major one I am dealing with. Last Friday 4/8 I drove it on a 30 mile or so trip, and every time before that, the car drove, idled, and accelerated as it was intended to.

I left it parked overnight outside, then Saturday morning I go to start, at first seems normal, then suddenly out of nowhere the car begins to chugg chugg, shake shake, and sound like just rough overall. When i give it gas, there is a little hesitation , and then when I turn lights, AC, fans, when I accelerate, the engine really begins to hesitate and bogg down.

The idle maintains ~700 RPM, in the sense, but the engine definitely feels off.

I've checked historic posts on similar conditions and can't quite pin point a similar situation, so I am posting this.

Just some background on my car and parts that may come to mind:

-New Delphi fuel pump over a year old
-New 02 sensor installed after this started happening -- apparently had no impact
-New alternator as of last night, but did not affect anything.
-Test/swapped all ECUs with known good ones -- had no affect. So I assume my Lambda, Idle, and ignition ECUs are working as intended.
-Test/swapped rpm relay, lambda relay -- had no affect. So I assume my relays are good.
-Test/swapped ignition coil -- had no affect. So I assume that is good.
-Checked idle speed motor is buzzing, checked frequency valve is buzzing, checked WOT switch is not sticking, checked idle speed switch is engaging. All seem good.
-Hooked up a dwell meter, besides doing a slight adjustment, I see my meter cycling up and down around the 20 mark (40 for 4 cyl reading), so I assume the fuel mixture is good and the cycling indicates lambda is working with 02 sensor and freq valve?
-Checked bulkhead connections are tight and cleaned.
-Battery tests good.
-Car starts quickly in cold or hot. Just idles like crap and there is hesitation on the accelerator while idling in cold or hot. More hesitation when AC , lights, are on to where it almost drops to die/shut off, but never actually does.

On saturday, I had to get my car towed because I was afraid it was going to shut off after driving it a few blocks. With everything on AC, fans, etc, the voltage seemed to drop at idle and felt like the car was bogging down wanting to die.


So at this point I have no idea what is going on. What gets me is that this started from one day to the next, not a gradual decline of performance or symptoms.
Trying to reach out to see if anyone has experienced this.

The only other thing that comes to mind is the CPR/WUR. Mine was working just fine, then this started happening. It is about 14 years old though. I assume it is still good, but I have a spare one I was going to swap to see . But like I said the car seems to start fine when cold but has slight acceleration delay when idle and idle sounds chugg chugg . The last time I replaced the CPR/WUR was 14 yrs ago, and I remember it was more gradual symptoms of hesitation on cold start up than actually it being an over night thing.

Anyways, I'm stumped at this point. I hate to say it is spark plugs, or anything else ignition related because it just happened over night for no reason.

Really appreciate any info,

Thanks!!

[Bitsyncmaster]

What is your voltage at idle?

Does is sound like a miss fire? The two pin connector from the pickup coil can oxidize because some get wet. Unplug and plug that in again. Also can do the same with bulkhead connectors. A sudden change is probably electrical. While your at it unplug and plug the ignition resistors.

[Beachdrifter]

What is your voltage at idle?

Does is sound like a miss fire? The two pin connector from the pickup coil can oxidize because some get wet. Unplug and plug that in again. Also can do the same with bulkhead connectors. A sudden change is probably electrical. While your at it unplug and plug the ignition resistors.

Hi Dave

It still sounds like it's running on all cylinders, just sounds rougher and deeper rumble than normal.

I disconnected and sanded the contacts on the coil, disconnected the bulkhead connectors. All tight and started it again with the same.

Battery is reading 12.5v cold. With car on normal 14v range. Even with all accessories on. Although the dash voltage gauge reads like 12.9v with car on and all accessories. It never seems accurate unless that is an indication of an electrical issue beyond battery or alternator voltage. Did the same with the resistor connectors and nothing changed.

Thanks.

[painterdave72]

How old are the injectors?? everytime i have worked on a Delorean its usually fuel related issues that cause misfires...

[Bitsyncmaster]

I would check your primary and control pressure. I have seen PPR o-rings fail suddenly but that is usually results in hot start problems. Have also seen the WUR get a dirty screen but would not think that would be a sudden change. The heater in the WUR can fail suddenly but that would only affect your cold running engine.

[Beachdrifter]

How old are the injectors?? everytime i have worked on a Delorean its usually fuel related issues that cause misfires...

Thanks, the last time I replaced FIs were around 2013. So I would suspect they are OK. But anything is possible.

[Beachdrifter]

I would check your primary and control pressure. I have seen PPR o-rings fail suddenly but that is usually results in hot start problems. Have also seen the WUR get a dirty screen but would not think that would be a sudden change. The heater in the WUR can fail suddenly but that would only affect your cold running engine.

Thanks Dave, so I gave it a go and decided to just swap out the CPR/WUR with a brand new one I had laying around as a test bench. Unfortunately it did not change anything. Worst case I have to hook up some gauges and see what my fuel pressures are.

I did notice that I waited about 4 mins for the car to heat up, and my dwell was stuck at 20 (40 for 4 cyl) the whole time, and it wasn't until I throttled it a bit that then it began to cycle and "hunt" as it usually does. Prior to that it seemed it wasn't trying to "hunt" idle on its own. I found that strange. Definitely I feel something is wrong here, but the freq valve was buzzing and I just put on a fresh 02 sensor so it must be working also.

[David T]

It may not be fuel related. The problem sounds like it could be old/bad ignition wires. Moisture from parking outside could have triggered this.

[Bitsyncmaster]

I did notice that I waited about 4 mins for the car to heat up, and my dwell was stuck at 20 (40 for 4 cyl) the whole time, and it wasn't until I throttled it a bit that then it began to cycle and "hunt" as it usually does. Prior to that it seemed it wasn't trying to "hunt" idle on its own. I found that strange. Definitely I feel something is wrong here, but the freq valve was buzzing and I just put on a fresh 02 sensor so it must be working also.

That seems a little long for warming up. I think what triggers closed loop is the O2 sensor warming up enough to start producing voltage. So taking that long suggests the O2 is running cooler for some reason. Now I would verify your getting the two grounds at the lambda ECU. Those two grounds go to the bulkhead connector and then get grounded at the engine block.

[Jonathan]

Bad gas? When was the last time you filled-up? Maybe your local gas station gave you half a tank of water with your gas.

[AugustneverEnds]

How old is your distributor cap? I had similar problems in 2017, turned out to be a bad cap with hairline cracks allowing moisture to seep in.

[Beachdrifter]

That seems a little long for warming up. I think what triggers closed loop is the O2 sensor warming up enough to start producing voltage. So taking that long suggests the O2 is running cooler for some reason. Now I would verify your getting the two grounds at the lambda ECU. Those two grounds go to the bulkhead connector and then get grounded at the engine block.

Hi Dave, this was in the realm of possibility, as I noticed about a week before all this happened my temp gauge needle pointed straight down, supposedly an indication of a ground issue. I used a paper clip to nudge it back up.

Now I admit electricity is not my strength. I understand tracing the lambda ground to the bulkhead connector (blue one? From the bulkhead connector diagrams floating around online i see it may be pin 23?)
, from there, could you please point out where physically the ground on the engine block is you are referring to?

Once there, how do I test a ground to see if it is "good enough "?

Really appreciate it
Thanks

[Beachdrifter]

It may not be fuel related. The problem sounds like it could be old/bad ignition wires. Moisture from parking outside could have triggered this.
Never thought of this, it was not raining and there was no dew that morning, so hopefully moisture wasn't an issue but something to keep in mind.

[Beachdrifter]

How old is your distributor cap? I had similar problems in 2017, turned out to be a bad cap with hairline cracks allowing moisture to seep in.

Hi Nick
It's as of 2005, so been awhile anything has been done back there. I hope not but if all else fails I may need to look deeper into ignition related stuff and take more stuff apart to get back there.

I should also say I've driven the car about 10k miles since 2005.

[Beachdrifter]

Bad gas? When was the last time you filled-up? Maybe your local gas station gave you half a tank of water with your gas.


This is true, well I added about 5 gals and that same day ran fine until next morning. I would say after driving 30 miles with that gas I did not observe any issues until next morning, so maybe the gas is not a problem.

Thanks

[Bitsyncmaster]

Hi Dave, this was in the realm of possibility, as I noticed about a week before all this happened my temp gauge needle pointed straight down, supposedly an indication of a ground issue. I used a paper clip to nudge it back up.

Now I admit electricity is not my strength. I understand tracing the lambda ground to the bulkhead connector (blue one? From the bulkhead connector diagrams floating around online i see it may be pin 23?)
, from there, could you please point out where physically the ground on the engine block is you are referring to?

Once there, how do I test a ground to see if it is "good enough "?

Really appreciate it
Thanks

I would pull the lambda connector off the lambda ECU and ohm out right at the pins on the connector to battery ground. Should be 1 ohm or less.

[Beachdrifter]

I would pull the lambda connector off the lambda ECU and ohm out right at the pins on the connector to battery ground. Should be 1 ohm or less.


Here's an update, appreciate everyone chiming in so far.
So I began once again to focus on the Lambda circuit.

- cleaned the pin 23, 24 on blue bulkhead connector, tested ground, both were good.

- cleaned idle microswitch contacts

- cleaned the ground and connector for the 02 sensor on back of the passenger side air intake manifold.

- found this on another thread:
"Disconnect the O2 sensor. GROUND the lead to the ECU (not the O2 sensor wire) and watch the dwell meter. Now connect a 1.5 volt battery between the ECU (+ to ECU, - to ground) and watch the dwell meter. Grounding should drive the dwell to full (85) and with the battery it should go to low (usually about 10). If this works the ECU is connected and working correctly."

Started the car and let the car warm up for 5 minutes. Just turned key, did not press any throttle. Car started right up as usual. Idle was still same and rough.

Performed the above test and both the lambda high and low was reached . So my lambda ECU is working fine.
With engine warm and lambda doing its thing, the dwell meter cycling average 20 (or 40 on 4 cyl scale) .

My next theory is something to do with the vacuum solenoid perhaps? That little copper looking gadget behind the fuel distributer? If this solenoid is bad would that result in symptoms I am experiencing? Also checked vacuum lines back there seem good.

Lastly, when I removed the electrical connector from that solenoid, and then restarted the car. I noticed a slightly better idle actually, but not 100% normal. Where is that electrical connector coming from?

Thanks,

[Bitsyncmaster]

Lastly, when I removed the electrical connector from that solenoid, and then restarted the car. I noticed a slightly better idle actually, but not 100% normal. Where is that electrical connector coming from?

Thanks,

One side of that connector gets 12 volts when the key is on. The other side goes to the idle speed switch and the idle ECU diode. The idle switch is grounded at idle and open off idle. So the solenoid passes vacuum on a warm engine when not powered.

[Rich]

My next theory is something to do with the vacuum solenoid perhaps? That little copper looking gadget behind the fuel distributer? If this solenoid is bad would that result in symptoms I am experiencing? Also checked vacuum lines back there seem good.

Lastly, when I removed the electrical connector from that solenoid, and then restarted the car. I noticed a slightly better idle actually, but not 100% normal. Where is that electrical connector coming from?

Additional to Dave's correct answer:

First, yes, the vac solenoid could be bad, either if it does not switch or if it has a leak. It has to switch open in order for the distributor vac advance to work (also requiring vacuum upstream of solenoid and a good distributor vac advance unit (https://store.delorean.com/102684-vacuum-advance-unit.html) downstream). Without this system working the engine will stumble when accelerating due lack of ignition advance. A large enough leak in the solenoid can affect the idle.

Second, the spades on the solenoid lead to each side of the solenoid winding. The black-blue wire on the plug goes to the idle speed switch and the idle ECU diode (in parallel to each other). The green plug wire is from Fuse 1. The connector itself has no polarity.

See this troubleshooting guide (https://dmctalk.org/showthread.php?18945) to bench test all functions of the vac solenoid. Also, it may be important that correct hose is connected to each port on the solenoid. Since your engine was OK before and you didn't pull those hoses just put them back on the same ports after testing. See the vacuum hose connection label under the engine cover in case you want to check.

[Bitsyncmaster]

See this troubleshooting guide (https://dmctalk.org/showthread.php?18945) to bench test all functions of the vac solenoid. Also, it may be important that correct hose is connected to each port on the solenoid. Since your engine was OK before and you didn't pull those hoses just put them back on the same ports after testing. See the vacuum hose connection label under the engine cover in case you want to check.

Yes it is important the hoses go to correct location because the distributor port vents when the solenoid is not feeding advance.

[Beachdrifter]

Yes it is important the hoses go to correct location because the distributor port vents when the solenoid is not feeding advance.

Rich,

Wow great info appreciate it. That bench test is pretty handy. I took the vacuum solenoid out. Performed the bench test, thankfully had everything I needed.

-hooked up 12 volts to the terminal and heard a click.
-with the valve still activated on 12 volts, attached a hand vacuum pump to center port, and it held vacuum.
-with the valve inactive, 12 volts taken off, the valve did not hold vacuum while plugging outer port. So per the bench test, failed #3.

Could this little bugger be all the heart ache?

I could attempt at this point doing a self fix by applying silicone to the base of connector as described in the bench test or order a new valve.

I actually used my own saliva as the "soapy solution " and at that point could hear the air sucking under the base of the connector.

Maybe we're onto something here or coincidence

Thanks

[Rich]

Maybe we're onto something here or coincidence



You found one of the two issues you can have with these. A vacuum leak in the connector seal or the body. Fixing it can help with an idle issue depending on how big the leak is.

That won't fix an issue with the vacuum advance. Seems like your solenoid passed the vac advance open/close test.

[Beachdrifter]

Here's an update,

So I played around with the vacuum solenoid, tried to do the temp fix on it but seems like it still leaks by. Anyways, I'm sure it's been doing that forever probably and likely isn't the cause of my rough running condition, but it was nice to know how that worked. So I ordered a NOS one from DMCH to put on later.

This morning I replaced the spark plugs anyways -- was a quick job and figured why not? It was time anyways and they looked like they needed replacing.

Started the car and still runs rough. Now I noticed a random infrequent backfire in the exhaust .

I think I've reached the point of giving up, because everything else related to vacuum advance, distributor, and anything else is beyond my skillset.
I may need to take it to DMCFL to have them give it a full look over. I'm very interested to see what this is that was caused over one night.

Basically, I give up. I admire those that have the original engine like me, but I'm seriously considering an engine swap or EFI conversion.
Any good shops in FL or any takers for a project like that? :)

[Rich]

Sorry it's been hard to get the engine back in shape there. This answer isn't about helping you with a fuel system swap.

It's another diagnostic question plus a recommendation for one more bit of possible troubleshooting. An easy test for the right shop.

a. Are you sure you are getting backfire at the exhaust? Not in the intake? Intake backfires are common if the engine is stumbling or misfiring badly on accel.
b. If it's in the intake then a (big) vacuum leak is high on the list of causes. That would fit with the other symptoms. If it's due to a failed component or vac hose connection then it could appear "overnight", too.
c. If it's verified as exhaust backfire then ignore this post. The only PRVs I've heard with exhaust backfiring were running with performance cams, backfiring only on hard decel.





T-shooting a vac leak: The simplest and best way to rule out or find a vacuum leak is with a smoke test. The best test will be done at a shop with a proper (>$1K) smoke test unit, very likely at DMCFL if you can't find somebody closer. Should take less than an hour including setup. The basic prep is pulling the air filter box off so they can seal the air intake on the metering unit.


....Started the car and still runs rough. Now I noticed a random infrequent backfire in the exhaust .

I think I've reached the point of giving up, because everything else related to vacuum advance, distributor, and anything else is beyond my skillset.
I may need to take it to DMCFL to have them give it a full look over. I'm very interested to see what this is that was caused over one night.

Basically, I give up. I admire those that have the original engine like me, but I'm seriously considering an engine swap or EFI conversion.
Any good shops in FL or any takers for a project like that? :)

[Ron]

Started the car and still runs rough. Now I noticed a random infrequent backfire in the exhaust .


Maybe try, pulling the plug wires one as a time while it is running. Listen for one that does not change the sound of the engine when you pull it.
(If you have one or more, it could be igniting fuel from misfires in the exhaust.)

===========

+1 on smoke test.

[Bitsyncmaster]

One last low cost thing to try is some injection cleaner in your tank of gas. That may help if something in you FD has gummed up.

[Beachdrifter]

Sorry it's been hard to get the engine back in shape there. This answer isn't about helping you with a fuel system swap.

It's another diagnostic question plus a recommendation for one more bit of possible troubleshooting. An easy test for the right shop.

a. Are you sure you are getting backfire at the exhaust? Not in the intake? Intake backfires are common if the engine is stumbling or misfiring badly on accel.
b. If it's in the intake then a (big) vacuum leak is high on the list of causes. That would fit with the other symptoms. If it's due to a failed component or vac hose connection then it could appear "overnight", too.
c. If it's verified as exhaust backfire then ignore this post. The only PRVs I've heard with exhaust backfiring were running with performance cams, backfiring only on hard decel.





T-shooting a vac leak: The simplest and best way to rule out or find a vacuum leak is with a smoke test. The best test will be done at a shop with a proper (>$1K) smoke test unit, very likely at DMCFL if you can't find somebody closer. Should take less than an hour including setup. The basic prep is pulling the air filter box off so they can seal the air intake on the metering unit.


Thank you Rich, appreciate your time and response. I actually took the spark plugs out again and readjusted gap to .028. I was a bit on the low side and think that was causing a random backfire. I'll restart the car tomorrow and see if that fixed it, probably was my wrong doing.

But if all else fails will take it to DMCFL for a good vacuum test.

In almost 20 years this is the first time the car has defeated me lol. I surrender.


Thanks.

[Beachdrifter]

One last low cost thing to try is some injection cleaner in your tank of gas. That may help if something in you FD has gummed up.

Thanks Dave, hey couldn't hurt, which one do you recommend? I heard seafoam is good?

Thanks

[Beachdrifter]

Maybe try, pulling the plug wires one as a time while it is running. Listen for one that does not change the sound of the engine when you pull it.
(If you have one or more, it could be igniting fuel from misfires in the exhaust.)

===========

+1 on smoke test.

Thanks Ron, will keep this in mind, when I pulled the new plugs again to adjust the gap, I saw they were all discolored slightly from use, so I assume each cylinder is firing.

[Jonathan]

I didn't read in detail all of the previous comments, but another random thing I've encountered on our cars is the air filter housing impeding the smooth movement of the air/fuel plate. I have found that if the plastic housing is not on straight, or is tightened down a little cock-eyed, it can make it hard for the plunger and plate to move freely/easily. So, a quick test would be to take it off completely and try and run the engine without it on, just to see how it is. It won't hurt anything if you're letting it idle in the driveway running without the filter.

[David T]

If you are going to try injector cleaner the one I recommend is Techron. Follow the directions. I doubt it will fix the problem but it can't hurt. The only way to fix a problem like this is to diagnose and troubleshoot in an orderly and logical sequence. Otherwise you wind up just throwing parts at it till you get lucky. You can fix things that way but it can get very expensive (and you waste a lot of good parts).

[louielouie2000]

My car is actually doing something very similar right now; it’s stumbling and tries to die while driving until it gets up to operating temperature. My entire fuel system was replaced about a year ago so I’m pretty baffled too. When I called DMCH they suggested I check the electrical connectors on the bulkhead and look for vacuum leaks. I ended up trimming up some of the vacuum hoses but still need to try hitting the vacuum components with carb cleaner while the car is running to see if there are leaks elsewhere. They suggested I do a CO adjustment after I check for electrical connections and vacuum leaks; my car is absolutely running way too rich. Sounds like any number of things can throw off your fuel mixture and cause these rough running issues. Good luck with your car and let us know what happens with it.

[Beachdrifter]

Thanks everyone for your insights.

I'm still troubleshooting this issue, although I haven't had much time during the work week.

I did throw in some techron, figured that couldn't hurt.

I also checked grounds again on the Lambda, and as many vacuum connections, they seem to check out for now. I understand a good smoke test will eventually come in handy, but I figured since this started overnight, maybe my vacuum hoses are fine.

What came to mind is disconnecting the thermo time switch to the cold start valve. I went ahead and disconnected that to see if my car would start. It started right up as it usually does. Which makes me wonder, is it possible that my CSV is stuck open or leaking fuel all the time, partially open perhaps, causing my new condition of rough idle, and rough engine running? Too much fuel getting in there making everything go haywire?

I could feel the car instantly run a little better when i first turned it on with the thermo switch disconnected -- car had been sitting for over 24 hrs prior.
Maybe I need to look into the CSV, pull it and see if it operates as intended, or get a test bench unit to test on.

Any thoughts on this?

Thanks,

[louielouie2000]

I’m pretty sure my issue is too much fuel, too. The engine seems like it’s drowning in fuel until it gets up to operating temperature and then it’s fine. I replaced the warm up regulator and nothing really changed. I didn’t realize cold start valves had gotten so rare & expensive; yikes.

[Bitsyncmaster]

What came to mind is disconnecting the thermo time switch to the cold start valve. I went ahead and disconnected that to see if my car would start. It started right up as it usually does. Which makes me wonder, is it possible that my CSV is stuck open or leaking fuel all the time, partially open perhaps, causing my new condition of rough idle, and rough engine running? Too much fuel getting in there making everything go haywire?

I could feel the car instantly run a little better when i first turned it on with the thermo switch disconnected -- car had been sitting for over 24 hrs prior.
Maybe I need to look into the CSV, pull it and see if it operates as intended, or get a test bench unit to test on.

Any thoughts on this?

Thanks,

The CSV only gets power when the starter is cranking. So pulling the TTS would only affect starting. I have found my car starts better in warm weather with the TTS disconnected. Now the CSV may have a mechanical defect in that it is not turning fuel flow completely off. You could test that putting the CSV in a jar with the engine running (you would need to plug the pipe where it was removed).

[Beachdrifter]

The CSV only gets power when the starter is cranking. So pulling the TTS would only affect starting. I have found my car starts better in warm weather with the TTS disconnected. Now the CSV may have a mechanical defect in that it is not turning fuel flow completely off. You could test that putting the CSV in a jar with the engine running (you would need to plug the pipe where it was removed).


Good info Dave, thanks.

Well I pulled the CSV and tested it with it disconnected and connected with car on. Both the valve and switch are working as intended, it squirted out fuel just on crank and is not leaking.


So onto the next theory... when I get one... lol.

I still can't believe this happened overnight. Perfectly running car one day, next day runs like it never ran good before.

The only thing I have pending is waiting for a nos vacuum solenoid I ordered since mine i know is bad. Other than that, perform a vacuum leak test, but still even that I don't understand how that could happen from one day to next.

Well to be continued.....where we're going we don't need roads, just jack stands and a garage!!

Lol..

[AugustneverEnds]

I'm sorry your issue is proving so elusive.

The more I read about your symptoms and what you have already verified the more strongly I feel you are having the same problem I did in 2019, a bad ignition cap and/or ignition distributor. My cap had barely visible cracks and when it was damp out (frequently in the humid summers in NY) the car would start fine but run erratically. Some of the problems were resolved when I replaced the cap but upon further inspection the dust cap/moisture shield in the distributor itself was cracked and moisture had become trapped in the body of the distributor. I had the distributor rebuilt in 2020 and the shop that did it found a considerable amount of corrosion especially on the impulse coil. After the rebuild all the issues were gone.

[Beachdrifter]

I'm sorry your issue is proving so elusive.

The more I read about your symptoms and what you have already verified the more strongly I feel you are having the same problem I did in 2019, a bad ignition cap and/or ignition distributor. My cap had barely visible cracks and when it was damp out (frequently in the humid summers in NY) the car would start fine but run erratically. Some of the problems were resolved when I replaced the cap but upon further inspection the dust cap/moisture shield in the distributor itself was cracked and moisture had become trapped in the body of the distributor. I had the distributor rebuilt in 2020 and the shop that did it found a considerable amount of corrosion especially on the impulse coil. After the rebuild all the issues were gone.

Thanks Nick, I'm starting to think this is leaning to a more difficult fix than what's on the surface. What you're describing makes sense . I can tell you mine is at least 17 yrs old. My car always stayed garage and rarely stayed parked outside over night. The day I drove it , it was fine. Then left it parked outside overnight, and next morning started with the rough idles and engine shaking all over the place, weak acceleration response.

Perhaps some morning dew, moisture made some things haywire back there. I've never done that job before and would mean the dive into the valley of death. That dreaded moment maybe it has to come to that.
I also want to say that in almost 20 yrs I've only driven the car like 10k miles, so maybe corrosion has built up in the cap that hasn't really had time to burn off or wear out.

Well, I will keep everyone posted, I will not end this thread until the solution is found.


Thanks,

[Beachdrifter]

Ok my friends,

Replaced vacuum solenoid with a perfectly operating one and no change.

After running out of options I decided to focus on the ignition system now. Early on in my diagnosis I replaced spark plugs, figured that was easy enough.
However that didn't change the rough idle condition or slow throttle response. I then started to get a popping sound in my exhaust, even though new plugs were gapped properly. This made me suspect my ignition was running weak and not burning up the fuel causing an enriched backfire in exhaust. But I didn't want to believe a weak ignition system just like that.


But now, I went ahead and bought an ignition spark tester and also one that is inline with a bulb.

I decided to perform this test as seen in the short video below:

https://youtu.be/IbzhxgD3ZUI

I did just the 3 plugs on the passenger side as a trial.

Per the video, any strong ignition system should pull "30" with a consistent spark. Well, mine didn't even spark at 30, and didn't start sparking until I reached 20.

I then hooked up the inline tester with a bulb, and the bulb flashed erratically, that per the product's packaging, "erratic bulb flashing is an indication of weak ignition system or fouled plugs".

Well, so previously I did a test and swapped my coil, it caused no difference so my current coil must be good.

Plugs are new.

That leaves based on the indications above that my ignition distributor system is failing in some way that is causing weak spark? Is the "30" expected for older based ignition systems like ours or more for electronic ignition? Not sure what the baseline for a normal running Delorean is.

Thanks!

[Beachdrifter]

Let me add, that the inline bulb test was blinking... maybe not really and indication that something was wrong since just consistent blinking is normal as I saw other videos.

I'm mainly interested if our ignition systems should be putting out a consistent 30kv or are the rated for 20kv?

Thanks

[Bitsyncmaster]

Whit your latest comments I'm thinking your cap is cracked or has moisture inside.

The spark plug gap sets the spark voltage. With our 0.026" gap I think 20 Kvolts is all you should expect.

It takes 30 Kvolts to jump a 1 cm gap. 1 cm = 0.039"

[Rich]

I agree the onset of the problem (wet, cold, overnight) also lines up with a cracked and/or dirty dist. cap. The condensing moisture can create a permanent or intermittent short circuit from one or more of the 7 high-voltage connections to ground or to any of the other connections.

There is a simple test as a starting point:

A spark "leak" problem at the dist. cap, which can happen with any conventional ignition system like this one, can often be observed in the dark. Arrange yourself and any components so you can see the distributor, then start the engine and just look all around it to see if there are any random sparks flashing across any areas on the exterior of the cap. You shouldn't see any.

This test doesn't prove a cap to be good, only to be bad. There can be sparks "leaking" to ground along the inside of a dirty or cracked cap.

And it is difficult to see any crack in a cap without looking very closely at all surfaces.

[Beachdrifter]

Thank you Dave and Rich.


So the more im reading about caps and rotors, the more im thinking I have to replace mine.

Maybe 17 yrs of corrosion or perhaps cracking is causing wacky stuff with the timing and sparks.

I guess just because one has sparks at the plugs doesn't mean the cap and rotor can't still be bad.
The corrosion or conductivity may be impacted to where current may be delayed to the cylinder causing a retarded spark and thus misfire, which leads to rich mixture, wobbly idle, and popping noises in exhaust. All of which im experiencing.

Will order a service kit and attempt this myself.
Will try to just remove fuel distributer, which I read seems doable for this job without removing air intake manifolds?

Thanks.

[Beachdrifter]

Oh and just to remove the curiosity about possible bad gas, I did drain the tank and refill with newer gas. No change in condition but at least ruled that out.

[louielouie2000]

It’s looking like my car simply had a big vacuum leak. The fat vacuum hose on the back of the warm up regulator was split because a hose clamp dug into it. I’ve driven it a few times since trimming the ends off all the vacuum hoses I could get to and the car is running smoother, quieter, and stronger than she ever has.

Moral of the story: may as well replace any vacuum hoses you can get to while doing your distributor cap!

[Beachdrifter]

It’s looking like my car simply had a big vacuum leak. The fat vacuum hose on the back of the warm up regulator was split because a hose clamp dug into it. I’ve driven it a few times since trimming the ends off all the vacuum hoses I could get to and the car is running smoother, quieter, and stronger than she ever has.

Moral of the story: may as well replace any vacuum hoses you can get to while doing your distributor cap!

Glad to hear it, thanks, I will check out the hoses and things while I'm in there!

[Beachdrifter]

Hi all,

So today I got in there to finally inspect this Cap and Rotor on the ignition distributor.

I removed the air mixture/fuel distributor to access the cap and rotor. Never had removed it before since owning the car. Was not too bad.
68390

Once out of the way, I could see the cap. I popped the cap off and I could see the rotor, below are the pics and the questions I have:

1. The cap with the plugs off. The only thing I saw was a small chip around the center coil plug hole. Otherwise looked fine to me.
68385


2. The cap closer, you can see the chip off the center hole. No cracks otherwise.
68386

3. The inside of the cap, no cracks I see. Looks pretty clean?
68387

4. Closer inside of cap, seeing the contact points and center coil contact. Maybe worn?
68388

5. Finally the rotor. The only thing I noticed was some green light corrosion on the center contact.
68389

So not sure what all this means, any feedback appreciated.
Since I am in there, I will order a new set of cap, rotor, and plug wires anyways since it's been 17 years since at least any of that stuff has been replaced.
I'll also check the condition of any other hoses in the area, any loose vacuum hoses, etc.

Here are my questions:


1. On the bottom of the fuel distributor , the "pipe of agony"? i think they call it, or also described as the idle air motor tube, is it normal for this tube to be kind of free to the touch and moves around gently? Seems like it is just inserted in there and nothing really holding it super tight. It's held by like a rubber grommet of some sort.

2. I haven't attempted to try to remove the rotor or inside dust cover, I assume what's under the cover should be good. I mean everything else looked clean. What is holding the rotor in place? do I just pull it out by hand? Haven't tried to mess with it yet. I heard you have to mark the position to insert the new one in the same place.

3. Anything else special about the rotor and cap reassembly that I should be worried about?

4. Is that vacuum advance something that I should worry about replacing? And if I do, can it be taken out without actually removing the entire distributor assembly shaft? Meaning is it as easy as just pulling it out and putting a new one in like the cap for example.


I'm praying and hoping that replacing the cap and rotor will fix my hesitation issue and rough idle, misfire, popping exhaust. If not, oh well, i did a good tune up after 17 years, but will be once again puzzled! Just taking it one step at a time.

Thanks all!

[Bitsyncmaster]

Cap and rotor look good in photos but in your first photo looks like some burning probably from the wires running over the cap. Defiantly don't want those wires on the cap. It may be sparking to the wires.

[AugustneverEnds]

How does the plastic shield under the rotor look? In your pic it seems ok but of course I can't see what you can. That was the one that really was the root of my troubles.

You may want to replace the pickup/impulse coil while you have things apart. I know it seems like the "while you're in there" list never ends but that little part can cause bundles of misery.

[Beachdrifter]

How does the plastic shield under the rotor look? In your pic it seems ok but of course I can't see what you can. That was the one that really was the root of my troubles.

You may want to replace the pickup/impulse coil while you have things apart. I know it seems like the "while you're in there" list never ends but that little part can cause bundles of misery.

Thanks, I took a peak under the dust cover as I haven't taken the rotor off yet, and it looks standard and clean from what I can see. When I get the rotor later this week and take it off, I will do a more detailed inspection. But I'm guessing and hoping it all looks ok.

[Beachdrifter]

More pictures, show and tell...

In an attempt to further eliminate any guess work on my part, I went ahead and finally after 17 yrs completed what is the rights of passage for any Delorean owner, I ventured into my Valley of Death. Figured why not, I'm so close to it, might as well finish taking that air intake off.

I was surprised the valley looks pretty clean, I have a bit of oil in the crannies , likely from a clutch slave I replaced a few years ago. I will clean it up before patching everything together. My vacuum connections seems pretty good, and rubber hoses were not cracking or brittle. So that checks. I also will assume all those switches and sensors in the Y pipe are good to go too, as I heard their failure rates are low. But if anyone has some neat way of checking them with a multimeter, please let me know.

68391

What I was mostly concerned about, was the condition of my intake ports on the engine and valves. Lots of black deposits caked all over the place. The engine has 44K original miles. Is there anyway to clean this stuff up on the surface at least at this point? I intend to use regular Techron cleaner from now on to help. But what is the general diagnosis on this type of condition? Although I don't believe this is the reason for my car not performing one day to the next, it is obviously a concern to me.

Here are pictures of my cylinder intakes:

68392

68393

68394

68395

68396

Finally, here is the inside of the air intake side, all black .

68397

[DMC-81]

Hi there,

While you have the intake off, double check your vacuum hoses. Another member had similar symptoms and it turned out to be a vacuum hose that looked normal but was not tight. It caused a vacuum leak and made the car run very rough and rich. This was a sudden onset of symptoms as well
Not sure if your problem is the same, but I would suggest changing all the vacuum hoses.

Also Robert said that sometimes the green vacuum switch (with 3 lines) goes bad.

Good luck

[Beachdrifter]

Hi there,

While you have the intake off, double check your vacuum hoses. Another member had similar symptoms and it turned out to be a vacuum hose that looked normal but was not tight. It caused a vacuum leak and made the car run very rough and rich. This was a sudden onset of symptoms as well
Not sure if your problem is the same, but I would suggest changing all the vacuum hoses.

Also Robert said that sometimes the green vacuum switch (with 3 lines) goes bad.

Good luck

Thanks Dana, good seeing you at Celebration. Car actually started acting up that Saturday morning and decided to tow it home that day rather than feel stranded on the road.

Good advice, coincidentally I started reading up more on that green switch and symptoms seemed similar of a bad one. I'll went ahead and ordered a new one from DMC.
Also got a coolant pressurizer to check for leaks before patching everything up.

Also will throw in some new vacuum lines while I'm in my VOD anyways.

This will likely take a few weeks, but will keep everyone posted. Thought about dressing up the engine too and maybe painting the air intake manifold. So making it a little project now.

Thanks.

[Beachdrifter]

Well, today I replaced the cap and rotor. Fairly easy (once everything is accessible). Inside of the distributor it looked pretty clean.
I also replaced the spark plugs, wires, and the thermal vacuum switch in the VOD. I heard those can go bad and since the plastic end seemed to rotate rather freely maybe I had a vacuum leak there . Worth replacing because the new one was firm, so maybe the old one was failing. Pressure tested coolant so seems good.

Anyways, as I started to plug the wires on the distributor cap, I noticed something odd. Previously to taking the wires off, I had numbered them and taken a picture, just to be on the safe side. Although I see the cap is numbered and it should correspond to the cylinder numbers on the engine block as well. In addition, the wires from DMCH were numbered the same as well, so how could someone mess that up? Well, I noticed my wires were crossed/swapped by the previous owner --- cyl 2 was plugged in the "3" cap position, and cyl 3 was plugged in the "2" cap position. I have been running my car like this since I have owned it for 17 yrs apparently!!! The engine ran perfectly (at least to me all these years). Does swapping 1 set of cylinders /plug wires make much of a difference ? Needless to say, I stuck to the number convention on the cap/block this time and we'll see how she runs when its all said and done.

I'm still working on it overall, decided to dress the engine up a bit with red silicone vacuum lines as well as do some painting.

Thanks for any insight.

[Ron]

Well, I noticed my wires were crossed/swapped by the previous owner --- cyl 2 was plugged in the "3" cap position, and cyl 3 was plugged in the "2" cap position. I have been running my car like this since I have owned it for 17 yrs apparently!!! The engine ran perfectly (at least to me all these years). Does swapping 1 set of cylinders /plug wires make much of a difference ? That would kill the two cylinders and at least 1/3 of your power, probably more...should of ran like dodo.

[DMC-Ron]

That would kill the two cylinders and at least 1/3 of your power, probably more...should of ran like dodo.

Exactly! It's difficult to believe two plug wires could be reversed and not be noticed. I would think the motor would run terrible! But I've never seen it done so maybe not. I'm curious to hear what you find.

Ron

68423

[Rich]

Exactly! It's difficult to believe two plug wires could be reversed and not be noticed. I would think the motor would run terrible! But I've never seen it done so maybe not. I'm curious to hear what you find.

Ron

68423

That's the very useful diagram out of the factory book. Good reference.
New users: This diagram is "upside down" since the flywheel/clutch is at the bottom and the pulleys are at the top (engine isn't shown in the orientation seen from the rear of the car).

[Beachdrifter]

Exactly! It's difficult to believe two plug wires could be reversed and not be noticed. I would think the motor would run terrible! But I've never seen it done so maybe not. I'm curious to hear what you find.

Ron

68423

Yes, I was very surprised. But after referencing the firing order in the manual and seeing your diagram, if 3 and 2 were swapped, would it have made much of a difference? As long as it maintains the left to right alternating firing order maybe it would have not been noticed. Now I can understand more if wires were swapped to where the alternating firing order was broken up causing two cylinders to fire back to back on one side.

But I'm no expert, all I can say was my car felt normal all these years and even took a trip to DMCFL a few years ago on unrelated work and they felt the car normal too.

Oh well, interesting find. I'm patching everything back together and hoping after all this when I fire her back up, she will be running back to normal. Otherwise it will be back to the drawing board or a trip on a tow to DMCFL.
We shall see in the next week or so and will let everyone know.


Thanks.

[Ron]

Yes, I was very surprised. But after referencing the firing order in the manual and seeing your diagram, if 3 and 2 were swapped, would it have made much of a difference? As long as it maintains the left to right alternating firing order maybe it would have not been noticed. Now I can understand more if wires were swapped to where the alternating firing order was broken up causing two cylinders to fire back to back on on.
If a plug wire is going to the wrong cylinder, that cylinder (and the cylinder the wire is supposed to go to) will fire at the wrong time, if at all.

[Bitsyncmaster]

If a plug wire is going to the wrong cylinder, that cylinder (and the cylinder the wire is supposed to go to) will fire at the wrong time, if at all.

The six plugs will all fire in sequence no matter where the plugs are. Now with two wires swapped, those plugs may fire at any of the four cycles of the stroke. I can't believe the engine would run without backfire or a blown exhaust with two wire swapped. Each cylinder still draws air and fuel on each intake cycle.

[Ron]

The six plugs will all fire in sequence no matter where the plugs are.???
I'm not sure why you replied with this -- I was talking about the cylinders firing, not the plugs.
I was trying to straighten out the "left"-"right" thing...


Now with two wires swapped, those plugs may fire at any of the four cycles of the stroke. I can't believe the engine would run without backfire or a blown exhaust with two wire swapped. Each cylinder still draws air and fuel on each intake cycle.+1!

...that or a break a piston or two.

[David T]

I have seen motors (not Deloreans) where the firing order was wrong and the motor did idle OK but under load it had a noticeable loss of power. Mileage was horrible too. Maybe you are incorrect, and the firing order was actually correct? In any case check and recheck it to make sure you have it right now.

[Beachdrifter]

IT'S ALIVE !!! FRANKENDELOREAN LIVES!!!

First, I have to say thanks to everyone who chimed in. I've been a member of the board since I owned my car back in 2005, and appreciate everyone's contributions.
I too have contributed over the years here and there, but life is busy and sometimes I don't do it often.

But when I have problems I come here, and I always make it a point to let others know how I fixed my issues to bring everything to closure, so others can benefit from it as well. In the 17yrs, this one has been the most challenging and hardest to figure out.

I will summarize what the issue was briefly for those that are new to the thread.
Early April I drove my car for about 30 miles (ran perfectly fine BTW), and left it parked overnight outside (was a special occasion, and the car never is parked outside overnight; it is always garaged). Next morning, the car started up fine, but throttle and idle was horrible. Had severe hesitation and the engine shaked a lot on idle. Just like that over 1 night the car started running like crap. I ended up towing it back home because upon driving, I felt like the car was going to shut off and the entire range of throttle response was just not right.

Over the next few weeks, I did diagnosis in 2 phases. I will describe the phases below which includes things I checked and reason behind it.

PHASE 1:

1. Electrical:
a. checked and cleaned bulkhead connectors. (i learned how dirty these can be over time and THEY DO sometimes fail to provide contact due to corrosion for current to
flow causing all sorts of problems)
b. swapped lambda ECU, idle ECU, ignition ECU with known good units for testing.
c. checked grounds on lambda, ran test on lambda to test 02 sensor responses.
d. checked fuses
e. unplugged and cleaned every connector in the engine compartment I could find.
f. changed alternator with new DMCH unit (unrelated, but I needed to do this anyways)
g. replaced 02 sensor
h. checked voltages at battery and car running
i. replaced spark plugs
j. checked spark at plugs, and at cables (all seemed to be good)

2. Mechanical:
a. swapped CPR/WUR with known good unit for test
b. Checked operation of idle motor
c. Checked proper operation of cold start valve (to make sure it wasnt sticking open)
d. checked operation of frequency valve
e. check for any loose vacuum hoses that were accessible.
f. drained fuel and refilled (thought maybe i had bad fuel?)
g. played around with the fuel mixture and dwell which caused my cat to glow for a few mins. probably was not the best idea to do that. so i stopped.
h. replaced the vacuum valve at the back of the fuel distributor since it appeared it had a leak.

After a few weeks of completing phase 1, it seemed that nothing had an affect on the condition. It still ran the same after doing all those things above. Even started chugging so bad it popped and crackled in the exhaust like it was angry at me or something.
I realized at that point that maybe I had to go deeper. I came to the realization that I needed to go into the VALLEY OF DEATH to slay my demon.


After a prayer or two, I rolled up my sleeves and got to work on the next part of the journey....

PHASE 2: -- VALLEY OF DEATH AND MORE...

Once you realize you have to go there, it's the mentality of "let me do that while I'm there anyways... " so at this point it was go for it all or go home.

a. Replaced cap and rotor (my 17 yr old one looked good enough to me, but did it anyways). inspected distributor inside for corrosion or obvious signs of problems
b. Replaced all new DMCH plug wires -- OK maybe I confused myself with the firing order issue i mentioned earlier. But you guys were right, there is only one way to go
and it is clearly marked. My car must have been fine even before i took them off, and I confused myself during the process.
c. Painted the air intake to chevy orange . Heck why not, I had to have a little fun with this too.
d. Cleaned/vacuumed the valley. Checked the engine block to make sure I wasn't rotting down there. Lots of nice little crevices to explore in the valley.
e. inspected fuel injectors and valves. Realized I should start using Techron on this car regularly on a 40+ old engine. Too much bad fuel out there.
f. inspected and replaced all vacuum lines (most of them anyways except the canister ones) with red silicone. Although I didnt see any cracked or obvious hoses that
looked like problems, maybe there was a leak somewhere I couldn't notice?

g. REPLACED THE GREEN THERMAL VACUUM SWITCH IN THE Y-PIPE -- Now, here is the ONLY thing I could attribute to anything that had to do with TEMPERATURE. Seeing I left the car outside and the drop in temperature maybe did something to this switch?? Don't know, but one thing I noticed when I inspected it was that I could rotate the green part with some moderate pressure while the unit was secured by the threads. That didn't seem right to me. Perhaps some seal in between the green casing and vacuum path was drawing a leak? When I installed the new one, it did NOT exhibit the ability to be rotated or moved. So obviously something was not normal with my old one.

68454

Took a deep breath, and patched everything back up slowly and to torque specs. I realized at this point if nothing in Phase 2 fixed my issue, then off to DMCFL would be for me.

After PHASE 2 was complete, my Engine looked like this:

68455

68456



Then came time to start her up. Naturally so, it took a few cranks to get her going. I figured the air in the fuel lines and fuel distributor needed to be purged before all the cylinders could get going . After a few minutes of cranking it and seeing her sputtering get better and better, she came ALIVE back to her normal self!!

THE HESITATION HAS GONE AWAY, THE THROTTLE RESPONSE IS BACK TO BEING IMMEDIATE UPON START UP AND ACROSS ALL LOADS IN WARM, THE IDLE IS A PURRR AT 750 WHERE IT SHOULD BE. THE ENGINE VIBRATION IS NORMAL AS IT SHOULD BE. NO POPPING , CRACKING, OR FUEL/RICH SMELLS COMING OUT THE EXHAUST, OR SMOKE.

SHE IS NORMAL AS FAR AS I CAN TELL. I let her idle and throttled it, testing responses for about 20 mins. All with full load of lights, AC, radio, and everything was normal.
Turned her off again, and started again, she ignited and idled perfectly.

OK, so mission accomplished as far as I see. Although I havn't taken her back on the road, it seems to be working fine.
I wish I was smart enough to be able to pinpoint the exact cause, but between that green thermal switch, replacing vacuum lines, and doing overall cap/rotor, did the trick.

THE ONE "BUT" ......
Now, the only thing I am noticing is that after even an extended period of warm up 15 + mins, the DWELL is STILL not moving (sticks to 20 on the 8 cyl scale). Couldnt get it to cycle. Everything on the car sounds good, like before, so maybe this is something I've had for awhile and never paid attention to it until now.
Is it ok to keep the car at this setting or should I look into this deeper? I can replace the 02 sensor again and see if that changes things?

Otherwise, the car seems to be running back to normal. THANKS!!!!

[Bitsyncmaster]

Congratulations on getting her running good. The frozen dwell first thing to check, is the FV buzzing? You can just jumper at the RPM relay connector the the double yellow/red wires to the brown and that will power up the lambda system and you should get 45 deg. dwell. No need to have the key on. That would be a good test for your dwell meter also. It may be your 20 deg reading (I guess your on 8 cylinder scale) is really 22.5 deg.

[Ron]

I'd suggest (re)checking the pulse ratios at D:04:15, 5 in the WSM.

P.S. Congrats!

:thumbup: Chevy orange.

[Beachdrifter]

Congratulations on getting her running good. The frozen dwell first thing to check, is the FV buzzing? You can just jumper at the RPM relay connector the the double yellow/red wires to the brown and that will power up the lambda system and you should get 45 deg. dwell. No need to have the key on. That would be a good test for your dwell meter also. It may be your 20 deg reading (I guess your on 8 cylinder scale) is really 22.5 deg.

Thank you Dave, Ron,

So I jumpered the RPM relay, key off, and I don't hear the freq valve buzzing. Just the fuel pump running. Also no reading on the dwell. I disconnected and played with the freq valve connector, and nada.

With the car on, i feel and hear a clicking / vibration / "buzz" from the frequency valve.

So with just the RPM relay jumped, I'm supposed to hear the freq valve clicking/buzzing? If that's the case, then something is definitely wrong somewhere and I am running open loop all this time I probably never knew it.

during phase 1 of my diagnosis I did the whole lambda test thing where you disconnect the 02 sensor, then ground the lambda to see the different readings on the dwell low to high reading (i dont remember the exact procedure), but anyways it showed my lambda ecu was working at least based on that test i assume.

Is this not electrical then and maybe I need a new freq valve?

[AugustneverEnds]

Congratulations, so happy to hear you won your battle!

Maybe you just need to clean the frequency valve, a cotton swab should do just fine.

Welcome back to the open road!!

[Bitsyncmaster]

Thank you Dave, Ron,

So I jumpered the RPM relay, key off, and I don't hear the freq valve buzzing. Just the fuel pump running. Also no reading on the dwell. I disconnected and played with the freq valve connector, and nada.

With the car on, i feel and hear a clicking / vibration / "buzz" from the frequency valve.

So with just the RPM relay jumped, I'm supposed to hear the freq valve clicking/buzzing? If that's the case, then something is definitely wrong somewhere and I am running open loop all this time I probably never knew it.

during phase 1 of my diagnosis I did the whole lambda test thing where you disconnect the 02 sensor, then ground the lambda to see the different readings on the dwell low to high reading (i dont remember the exact procedure), but anyways it showed my lambda ecu was working at least based on that test i assume.

Is this not electrical then and maybe I need a new freq valve?

I'm guessing you jumped the fuel pump at the RPM relay unless you have a three pin jumper and jumped both the fuel pump (white/purple), double yellow/red and the brown.

You just need to jumper the double yellow/red to the brown to get the lambda buzzing, no key required. If that does not get it buzzing you now need to troubleshoot why.

[Beachdrifter]

I'm guessing you jumped the fuel pump at the RPM relay unless you have a three pin jumper and jumped both the fuel pump (white/purple), double yellow/red and the brown.

You just need to jumper the double yellow/red to the brown to get the lambda buzzing, no key required. If that does not get it buzzing you now need to troubleshoot why.


Dave thank you. Silly me, now I remember why I had kept a 3 prong jumper in the relay compartment.

So yes, I jumpered all 3 and got the frequency valve buzzing strong, plus dwell reads steady 24.5 at the same time.

So looks like we established that. I assume that means my lambda curcuit should be working ? I also figured I'd swap in a new 02 sensor just in case.

Hmm , What else could be driving the fixed dwell while the car is on ?

[Bitsyncmaster]

Dave thank you. Silly me, now I remember why I had kept a 3 prong jumper in the relay compartment.

So yes, I jumpered all 3 and got the frequency valve buzzing strong, plus dwell reads steady 24.5 at the same time.

So looks like we established that. I assume that means my lambda curcuit should be working ? I also figured I'd swap in a new 02 sensor just in case.

Hmm , What else could be driving the fixed dwell while the car is on ?

Yes your lambda is working. If it still holds steady on a hot engine then I guess your O2 is bad or disconnected.

[Beachdrifter]

Yeah I was looking into some previous forum posts seeing if possibly its my lambda thermal switch that's giving me a fixed reading. I know my WOT switch isn't stuck because when I press it I can see the change in dwell.

If I disconnect the thermal switch in the y pipe can that just eliminate the possibility of getting and override signal to the Ecu and just let the 02 sensor do its thing?

Dang, I should have replaced that thermal switch while I was in there maybe.

[Bitsyncmaster]

Yeah I was looking into some previous forum posts seeing if possibly its my lambda thermal switch that's giving me a fixed reading. I know my WOT switch isn't stuck because when I press it I can see the change in dwell.

If I disconnect the thermal switch in the y pipe can that just eliminate the possibility of getting and override signal to the Ecu and just let the 02 sensor do its thing?

Dang, I should have replaced that thermal switch while I was in there maybe.

Yes you can try to disconnect that wire going to the thermal switch or going to the lambda ECU. Not sure if you can pull the pin in the ECU connector. Or just cut the wire somewhere that can be connected together later.

[Beachdrifter]

Yes you can try to disconnect that wire going to the thermal switch or going to the lambda ECU. Not sure if you can pull the pin in the ECU connector. Or just cut the wire somewhere that can be connected together later.

You were right, I figured the only other option was to get rid of the overrides from the WOT switch or lambda thermal switch.

So I figured I'd just eliminate the feed of those both into the lambda ecu pin 7 by snipping that light green wire inside the ecu connector. I'm in Florida and don't see the point of the lambda thermal switch and I don't intend to be speed racer with my Delorean any time soon, so I should be ok.

After cutting that wire, I started the car and after a few minutes the dwell started to cycle. I was a bit on the high side so I brought it down closer to 20. Now it is bouncing around anywhere between 15 and 24. Not the best cycle , and seems to be intermittent at that, but oh well I'm done with asking for perfection. I left the adjustment at that since it seemed to be averaging around 20ish. It's tuned better than it was before at least and I was afraid to mess with it anymore.

Looks like my thermal lambda switch needed to be replaced when I was in the VOD, but I missed it. Oh well, I love my car, but I'm not going back in there just for that. Being iM in Florida , I'm not too worried about it. If I ever think I need it I could rig a timer switch to the wire to simulate a ground for a few minutes then open or just replace the thermal time switch when I'm in the VOD hopefully not for a looong time.

At least my car is no longer stuck in open loop.

So as they say in the movie business, I guess that's a wrap!!!

Car runs great now and that little dwell thing is taken care of.

I learned a lot from this experience.

[Bitsyncmaster]

Congratulations on getting her fixed.

I worked on a friends car that had very excessive hunting when extremely cold warmup. It only did it when I had it parked in 20 deg. F. temps or below. It turned out cutting that light green wire to the lambda ECU fixed the problem. So even though the mixture was adjusted to book values that rich mixture in very cold weather was to much for it to handle. My car did not have that problem however.

Anyway I don't think many owners would ever experience the need for that lambda thermal switch.