High Idle, and Tightening the Distributor

[jangell]

Finally getting close to actually driving my car again. I only get a few hours every week or two to work on it (next time is going to probably be January 7th), so it's been taking a while.

The current problem is that the car is idling at over 1500 RPM when the distributor is set to 13 degrees, but it idles properly at 0 degrees (although the response is very sluggish at that position). I have Ed Uding's performance cams in here (that's, Josh!), but as I recall the timing is the same with them. Beyond that and Josh's exhaust upgrade, the engine is stock.

My more knowledgeable (on non-DeLoreans, anyway) friend and I didn't notice any obvious vacuum leaks, but that doesn't mean we didn't miss some. We also wondered if the idle motor was to blame. As a test, we disconnected the plug on the motor, and then white bulkhead connector itself, and saw no significant change (maybe a very slight shift at the instant it was disconnected, but that's it). We confirmed the idle motor was working by applying 12v to the middle pin and ground to either outer pin. We also confirmed that the ECU is sending a signal to the idle motor, in so much as we had 12v and ground on two of the pins on the connector. We confirmed the idle microswitch is depressed, although it occurs to me that we didn't actually test it to make sure it was working...

Anyone have any tips on diagnosing a high idle?


Second question: We cannot figure out how to secure the distributor once we've tuned it in. All the fuel, vacuum, etc. hoses are in the way, so we can't clamp it down. Is there some trick to this? At worst, we could mark the location and move the fuel system or the entire manifold, but we'd really like to avoid that, and it doesn't seem like it should be necessary.


I've also been tempted to not tune it and just go ahead with the EFI conversion I've been planning, but I'd sort of like to drive it for a few months before I embark on another project. :)

Thanks!

-- Joe

[Bitsyncmaster]

Do you have the curb idle screw backed out? Make sure the idle set screw does not stop you from backing out the cure idle screw. Are all three brass bypass screws closed? Try pulling the distributor advance hose and see if the idle comes down.

[jangell]

Do you have the curb idle screw backed out? Make sure the idle set screw does not stop you from backing out the cure idle screw.

I found references to this when I googled for high idle discussions yesterday, bit I wasn't actually sure what the curb idle screw was. I thought it was the one on the idle switch, but that seems to be engaging the switch properly (we didn't mess with it when we took the engine apart). Your comment makes me think we were looking at the wrong thing.


Are all three brass bypass screws closed?

This I did confirm -- all three screws are closed.


Try pulling the distributor advance hose and see if the idle comes down

Ah, we didn't try that. I'll have to give that a shot.

Unfortunately, it'll be three weeks until I can try it out (out of town for the holidays, and the car is 2.5 hours from where I live anyway). I'll be sure to actually post my results as soon as we do any tests.

Thanks!

-- Joe

[Bitsyncmaster]

The curb idle screw is the one below the idle switch screw. In most cars you set the curb idle to 500 RPM. It's not recommended to back it out fully because the throttle plates may stick or scratch the throttle bores.

Engine idle usually has the problem when the engine is hot (oil is thin) and no loads (AC or headlights) are running. That is when you want to adjust your curb idle. It must be set below the idle ECU closed loop speed (775 RPM). If not then the idle motor will just fully close and would not be controlling idle speed anymore.

[Henrik]

The curb idle screw is the one below the idle switch screw.

What are the part numbers of these screws? I assume they are the ones on the inlet manifold but I wanna make sure. Also, once I locate them, is there a process to follow? I have high idle when the engine is warm so I think this may be where my problem lies.

[Bitsyncmaster]

What are the part numbers of these screws? I assume they are the ones on the inlet manifold but I wanna make sure. Also, once I locate them, is there a process to follow? I have high idle when the engine is warm so I think this may be where my problem lies.

No. The curb idle screw is the lower one on the throttle arm. The upper one is the idle switch screw. I will post a photo after my camera charges.

[Elvis]

How did the idle speed change when you applied +12V to the center pin and ground to the outer pins ?

In one position idle has to go up and on the other position the engine should shutt off.

Did it do that ?

[Bitsyncmaster]

The lower screw shown on the throttle arm (not the brass screws) is the curb idle adjustment. Just back it out until it does not touch and then turn it in about a 1/4 turn.

[jangell]

How did the idle speed change when you applied +12V to the center pin and ground to the outer pins ?

In one position idle has to go up and on the other position the engine should shutt off.

Did it do that ?

We didn't actually try it when the engine was running -- we should have, though. We were just making sure the motor worked at all. I'll try that next weekend (which is the next time I'll be able to work on it). Thanks!

-- Joe

[jangell]

The lower screw shown on the throttle arm (not the brass screws) is the curb idle adjustment. Just back it out until it does not touch and then turn it in about a 1/4 turn.

Thanks! I'll check it next weekend and report back.

-- Joe

[jangell]

Got a late start today, so I didn't have a chance to try everything suggested here. I got the spark timing set, but then got distracted by the headers glowing red after a few minutes.

We double checked for vacuum leaks and didn't find any. We confirmed the frequency valve is buzzing (both by jumping the RPM relay and by hearing the engine change when it was unplugged). We disconnected the cold start value in case it was sticking on, but there was no difference. We tried to lean out the mixture, but that didn't seem to help either, although it got us down to 1000-1200 RPMs. Both the idle screw and curb idle screw seem to be properly adjusted, and the idle switch is engaged when the throttle is out.

So, any tips for diagnosing glowing headers? It seems like the car is lean, but I'm not clearl on how to diagnose it at this point. This car has Ed Uding's cams and DeLorean Performance Industries' exhaust. If I can't figure it out in the next week or two, I might just go ahead with the EFI upgrade sooner than planned, since there's little point in spending a lot of time troubleshooting K-Jet if I'm just going to replace it anyway.

Thanks!

-- Joe

[DMCTek]

How long have you had this high idle? Was it present right after the cams and exhaust were completed?
Do your headers glow at idle or just when held at higher rpm?

[opethmike]

Got a late start today, so I didn't have a chance to try everything suggested here. I got the spark timing set, but then got distracted by the headers glowing red after a few minutes.

We double checked for vacuum leaks and didn't find any. We confirmed the frequency valve is buzzing (both by jumping the RPM relay and by hearing the engine change when it was unplugged). We disconnected the cold start value in case it was sticking on, but there was no difference. We tried to lean out the mixture, but that didn't seem to help either, although it got us down to 1000-1200 RPMs. Both the idle screw and curb idle screw seem to be properly adjusted, and the idle switch is engaged when the throttle is out.

So, any tips for diagnosing glowing headers? It seems like the car is lean, but I'm not clearl on how to diagnose it at this point. This car has Ed Uding's cams and DeLorean Performance Industries' exhaust. If I can't figure it out in the next week or two, I might just go ahead with the EFI upgrade sooner than planned, since there's little point in spending a lot of time troubleshooting K-Jet if I'm just going to replace it anyway.

Thanks!

-- Joe

Trust me on this - get any and all known problems with your car sorted out first; before going EFI.

[jangell]

How long have you had this high idle? Was it present right after the cams and exhaust were completed?

I just installed the new cams and exhaust. The car's been in the garage for 14 months now as I learned how to remove the old exhaust, removed the heads and had them resurfaced, installed the performance cams, put it back together, replaced a transmission drive flange (apparently I should have done both, since the other side is leaking now), replaced the rear lower link arms with adjustable ones, and repairing the hub carrier that snapped when doing the former.

So, this is the first time the car's been running with the next exhaust and cams. The car has yet to be on the road with this setup.


Do your headers glow at idle or just when held at higher rpm?

This is more or less at idle. I say "more or less" as we're still trying to get the idle tuned in. The first thing we did was adjust the spark timing, at which point the car idled at around 2000 RPMs. It seems to be running very rough when we lean out the mixture to get it down to ~800 RPMs.

Unfortunately, I didn't have much time to play with it this weekend, so I wasn't able to try as much as I'd have liked to. I'm hoping to make more progress this coming weekend.

Thanks!

-- Joe

[jangell]

Trust me on this - get any and all known problems with your car sorted out first; before going EFI.

I was going on the theory that since everything seemed to be working properly except the fuel metering system, it might not be worth the effort to get K-Jet working just to rip it off again in a few months anyway. Even so, I'd prefer to drive it for a bit before I embark on the EFI conversion, so it's kind of a tough call.

-- Joe

[David T]

If the exhaust manifolds (headers) are glowing red you are running WAY too rich. Unburned fuel is getting into the exhaust and burning in there. It may be possible the CSV is leaking, leaking, bad spray pattern on one or more injectors, plunger in the mixture unit sticking, CPR stuck, etc. You need to figure out how the extra fuel is getting into the motor. I agree the best way to go to EFI is the get the motor running well stock to rule out any underlying problems BEFORE you change things and then have to wonder if you caused a problem or it was there BEFORE you started making changes. Starts with the basics, oil pressure, Cylinder pressure tests, balance tests and leak-down tests. Adjust the valves, clean and gap the plugs. Get the basic mechanicals in the best condition you can. Since you had the heads off it is *possible* you have the cam timing off. That can also cause glowing headers. Recheck it.
David Teitelbaum

[jangell]

If the exhaust manifolds (headers) are glowing red you are running WAY too rich. Unburned fuel is getting into the exhaust and burning in there. It may be possible the CSV is leaking, leaking, bad spray pattern on one or more injectors, plunger in the mixture unit sticking, CPR stuck, etc. You need to figure out how the extra fuel is getting into the motor.

What's the best way to test the CSV for leaks? Just take it off and run the fuel pump?

Is testing the CPR a matter of applying 12v and seeing if it makes a sound?

I imagine I can test the plunger on the mixing unit and check the injectors at the same time by pulling the injectors, running the fuel pump and checking the fuel spray, and then pushing the metering plate (venturi, whatever it's called) and seeing if the amount of fuel changes?


I agree the best way to go to EFI is the get the motor running well stock to rule out any underlying problems BEFORE you change things and then have to wonder if you caused a problem or it was there BEFORE you started making changes. Starts with the basics, oil pressure, Cylinder pressure tests, balance tests and leak-down tests.

Yeah, I guess getting that stuff figured out now with the stock fuel system would help us figured out if we screwed up anything putting it back together. I don't really want to buy NOS fuel system parts to replace broken ones, although knowing that they ARE broken would be very helpful, and probably worth replacing if it's not overly expensive so I don't find out they're masking a more significant underlying problem.


Adjust the valves, clean and gap the plugs. Get the basic mechanicals in the best condition you can. Since you had the heads off it is *possible* you have the cam timing off. That can also cause glowing headers. Recheck it.

The good news is that we adjusted the valves and redid the cam timing from scratch when we put the engine back together, so we're pretty sure that's good (we screwed up the timing a couple times before getting it right). However, that doesn't mean it actually is right. Not that I really want to pull everything off the valve covers to check the valve timing again, or remove the exhaust to get the timing cover off...

Thanks!

-- Joe

[David T]

Pull the CSV and hang it in a cup while applying fuel pressure. It should not pass any fuel, you can unplug the electrical connector to make sure there is no power on it.
To test the CPR you need a fuel gauge set-up to watch the pressure as the motor heats up and compare it to the chart in the Workshop Manual. You should also verify all of the fuel lines are correctly hooked up before.
You can check the plunger and injectors by appyling fuel pressure and moving the air sensor plate. Pull the injectors and stick them all in cups.
With the fuel pressure gauge you can also check the Primary Pressure Regulator. If it is stuck or set too high you will get too much fuel too.
David Teitelbaum

[jangell]

Pull the CSV and hang it in a cup while applying fuel pressure. It should not pass any fuel, you can unplug the electrical connector to make sure there is no power on it.
To test the CPR you need a fuel gauge set-up to watch the pressure as the motor heats up and compare it to the chart in the Workshop Manual. You should also verify all of the fuel lines are correctly hooked up before.
You can check the plunger and injectors by appyling fuel pressure and moving the air sensor plate. Pull the injectors and stick them all in cups.
With the fuel pressure gauge you can also check the Primary Pressure Regulator. If it is stuck or set too high you will get too much fuel too.
David Teitelbaum

Thanks! Now I just need to find a fuel pressure gauge. :)

-- Joe

[jangell]

OK, here's the update:

With the RPM relay jumped to run the fuel pump:
- Fuel lines are correctly mounted and running to the right cylinders from the distributor
- CSV does not leak
- Injectors have good spray
- Pushing the air sensor plate cleanly changes the pressure to the injectors
- System pressure (per Workshop Manual D:02:02, and Volvo CI Fuel System Manual part B15) is 70 PSI
- CPR pressure when cold is ~12 PSI
- CPR pressure when hot is ~45 PSI (tested by jumping the fuel pump and frequency valve/CPR pins at the RPM relay and waiting ~5 minutes, although I didn't watch that timing too closely)

The hot CPR pressure seems a little low, but not horribly so.

We're quite sure that the valve timing and clearances are correct, as we spent a fair bit of time getting that right before putting the timing and valve covers back on. Specifically, we used the Volvo manuals to completely redo the valve timing, and set the valves to 0.007".

Assuming the CPR is close enough, everything seems good. I'm not sure what to check next.

Thanks again

-- Joe

[jangell]

Another update: We tried setting the ignition timing again. This time we remembered to disconnect the vacuum advance first. However, the cats still glowed at 10-13 degrees BTDC. The car also idled high, at about 1500 RPM. When we let the distributor slip to ~3 degrees, the car idled closer to ~800 RPM, but did so rather roughly.

We tried leaning out the mixture 1/4 turn, but this caused a lean misfire and finally the engine died. We then went back to center, and then another 1/4 turn rich. It ran smoothly, but with an even higher idle and quickly caused the headers to glow.

We think the curb idle might have been slightly off, leaving the throttle plates very slightly open. Of course, we lost the 2.5mm allen wrench while we were working on this and weren't able to test this adjustment yet. It'll have to wait until next week.

I'm not sure if this information helps any with the diagnoses. Thanks again for the assistance!

-- Joe

[DMCTek]

Valves should be set at .004" intake and .010" exhaust. Might make a bit of noise on the intake side, but should not cause a running issue.

A rich mixture will actually keep combustion temps down, rich will cause the cats to glow red but not the header inlets.

You really need to check fuel pressures with a proper guage set and then set c.o. with a dwell meter reading the frequency valve.

Personally I think you are chasing a vacuum leak.

Good Luck!

[Delorean Industries]

Valves should be set at .004" intake and .010" exhaust. Might make a bit of noise on the intake side, but should not cause a running issue.

A rich mixture will actually keep combustion temps down, rich will cause the cats to glow red but not the header inlets.

You really need to check fuel pressures with a proper guage set and then set c.o. with a dwell meter reading the frequency valve.

Personally I think you are chasing a vacuum leak.


Good Luck!

.007 on our camshafts exhaust and intake. He is running a set of our camshafts grinds. Same recommendation as posted on a cam sheet from DMC-CA as well for base cut camshafts. Too tight on on a ground camshaft and it promotes float at higher rpms. You are right though Mike for a stock cam or even a less aggressive cut like in a stage II.

[DMCTek]

.007 on our camshafts exhaust and intake. He is running a set of our camshafts grinds. Same recommendation as posted on a cam sheet from DMC-CA as well for base cut camshafts. Too tight on on a ground camshaft and it promotes float at higher rpms. You are right though Mike for a stock cam or even a less aggressive cut like in a stage II.

In that case wouldn't the exhaust side promote float if the stock setting is .010" and they are set to .007" (tighter).

[Delorean Industries]

It is a matter of it being excessively tight. At .007 you are fine on the exhaust side. At .004 or less once hot the clearance decreases and causes issues on a base cut camshaft (which all performance DMC camshafts are except for ones cut from blanks)

You wouldn't think this could be such an issue but it is most evident as a misfire at higher rpms or by your wide band going excessively lean. I pulled my hair out trying to figure this out years ago. The solution was the valve clearance.

[Ron]

Two things, maybe just the way I'm reading it tho:

The hot control pressure seems too low to me, what ~10% below specs.
Hard to tell with the cold...what temp was it?

It sounds like you can't get it to idle down to 750 RPM (required to set the timing correctly).

[Elvis]

I bet you still haven't tested the idle motor like I asked you lately - but with running engine.

high idle means it gets too much air thru some hole.

throttle plates - curb idle and valves on the plates
those 3 brass screws not tight ? (don't break them)
idle motor not closing all the way - dirty or rusty?
idle ECU - broken ? happens - not often but happens.
temp sensor broken ? - I had such a problem lately, the connector was dirty / oxy...
(open temp sensor means the ECU regulates idle up to ~1500rpm)
ilde switch not pushed ?
the vacuum valve must work or it has too much advance and won't go down to 800rpm.

even if the mixture is off or advance is a bit higher - idle has to go down if it doesn't get air. I expect it is metered air, not even a vacuum leak. -> Idle motor, sensor and ECU !!!!!

[jangell]

You really need to check fuel pressures with a proper guage set and then set c.o. with a dwell meter reading the frequency valve.

The good news is I had one: an OTC 6550 Master Fuel Injection Kit from Amazon. That's how I got those numbers in the first place. :) I didn't check the CO and the Lambda system; I'll have to grab a dwell meter (my multimeter doesn't have that) and do that next weekend. Looks like I'll be following D:04:01 in the Workshop manual... although that does say I need an IR exhaust gas analyzer, which is going to be out of my price range. The steps also imply that I should already have the car idling properly before I do this.


Personally I think you are chasing a vacuum leak.

I thought we had those cleaned up, but it won't hurt to check again. It's quite possible that I just don't know where all the common leak locations are and overlooked something (I'm basically making this stuff up as I go along, following the manuals and bugging all of you for help :) ). I'll do that next weekend to.


Good Luck!

Thanks!

-- Joe

[jangell]

The hot control pressure seems too low to me, what ~10% below specs.

I was wondering about that as well. It does seem low, but it didn't seem so low that I wouldn't be able to get a somewhat reasonable idle (I mean, as opposed to it not working at all). But then, I really don't know how the car would behave if the CPR was running below spec on an otherwise perfectly tuned car, so my intuition is probably way off.


Hard to tell with the cold...what temp was it?

It was about 35-40 degrees in the garage that day, and the engine hadn't been started yet. I should have mentioned that -- that certainly seems like it could affect the cold readings. I'm not sure how much it would affect the hot readings due to the heater in the CPR -- I really have no idea.


It sounds like you can't get it to idle down to 750 RPM (required to set the timing correctly).

Correct -- it seems to be at about 750 RPM when we let the timing slip to ~3 degrees, but if we bring it up to 13 degrees it shoots up to 1500-2000 RPM. I assumed we need to set the timing before we can get the RPMs down, right.

Thanks!

-- Joe

[jangell]

I bet you still haven't tested the idle motor like I asked you lately - but with running engine.

I honestly can't remember now. Let's assume I didn't. :) I'll do that test next weekend, just to be sure.


high idle means it gets too much air thru some hole.

throttle plates - curb idle and valves on the plates

I think these are slightly open; I have to pick up another allen wrench to adjust the curb idle screw a bit. It's very slight, though.


those 3 brass screws not tight ? (don't break them)

I know these are all tight, but I'll re-verify to be sure.


idle motor not closing all the way - dirty or rusty?

I'll verify this as well. How would I know that it's closing all the way? I know it's doing SOMETHING when I apply 12v, as I can hear it click opened and closed.


idle ECU - broken ? happens - not often but happens.

I saw some diagnostics instructions in the Workshop manual; I'll go through that next weekend as well.


temp sensor broken ? - I had such a problem lately, the connector was dirty / oxy... (open temp sensor means the ECU regulates idle up to ~1500rpm)


This is the thermistor on the the Y pipe under the intake manifold? I see it mentioned in the Workshop Manual, D:05:02. I believe that is new, but it's been months and I'm starting to lose track of these things. Kinda a PITA to get to at this point, but I'll check it out, since that does correlate with the high RPM we're seeing. Hopefully I can just tap the wire at the ECU and check the resistance before tearing the manifold apart again.


ilde switch not pushed ?

I confirmed that it is being pushed.


the vacuum valve must work or it has too much advance and won't go down to 800rpm.


even if the mixture is off or advance is a bit higher - idle has to go down if it doesn't get air. I expect it is metered air, not even a vacuum leak. -> Idle motor, sensor and ECU !!!!!

I'll take a thorough look at these this weekend. Thanks!

-- Joe

[dmc4087]

I'm chasing a very similar problem to you. My engine has just been rebuilt.

I did a vacuum leak test on my engine last week - found leaks on a few injector seals (didnt change these), the brass screws not tight enough, and the air horn seals (new gaskets but it must need a bit of sealer too.)

Once the parts arrive, I'll get them fitted and let you know how my idle behaves.

[jangell]

What techniques did you use to hunt down those leaks?

Thanks

-- Joe

[Elvis]

Usually the brass screws don't need to be closed completely, but in this case you
need to do it to find where the air comes from.

Vacuum leaks usually will make the idle hunt ! does it ?

Please set timing to the correct position, but the following tests can still be done.

Vacuum valve:
do you have a small hose that fits the valve ? you have to blow or suck air thru it.
pull one of the hoses and attach your test hose.
engine off - the valve should be closed.
turn the key to the on position - engine can stay off.
suck/blow again and play with the trottle. at the idle position it should be closed and
when moving the butterflies the valve has to open.
Put it back together.


Idle Motor (is also a valve or a tap !):
Take off the connector
Apply +12V at the center spade of the motor
Then apply GND to one of the outer pins as you did a few days ago or weeks,
but this time with engine running !
GND on one side will rise idle to max, on the other pin it should close the valve
completely and the engine has to die. If it doesn't and idle stays up - motor/valve
might be faulty or it is another air source.

If engine dies - you know the valve is OK - then let's play with the ECU and test the
temp sensor.
Do you have a Multimeter ? get one ! a cheap one is OK.

Engine off:
Do you know where the idle ECU is located ?

There are two connectors. We need Pin 9 and 11.
Pull the connector and measure the resistance - then tell me.
Put the connector back on and take a short piece of wire and bridge Pin 9 and 11.

Engine on:
Does idle go down ?
Yes ? Temp sensor or one of the connectors faulty.
No ? ECU faulty or it still gets air from somewhere else.

like always - it takes me 3 times longer to type all this stuff then I need to test it.


have fun, I haven't seen my car for weeks :-()

[jangell]

Thanks for all the great info Elvis! I'll be sure to go through the steps this weekend and report back with what I find.

-- Joe

[dmc6960]

There was a person I had helped lately that had a glowing CAT. Turned out the the plug wires for cylinders #1 and #2 were reversed on the distributor. Perhaps you should double check your ignition lines.

[jangell]

Here's the latest batch of diagnostics. The short version is that everything appears to be working, but the idle is still high and the headers still glow.

Ignition timing set to 13 degrees.

Distributor Vacuum Advance:
- Passes suck test (advance is clearly changing when sucking/blowing on the vacuum line)
- Valve actuates when when key is on (engine off) and trottle is manipulated
- Conclusion: Vacuum advance is working properly

Temperature Sensor:
- ~5000 ohms cold (engine cooling for about 1/2 hour, likely higher if the engine was completely code).
- ~1200 ohms hot (can't say how hot; this should not be taken as the properly calibrated reading, but it does show the range and that it is reacting to temperature changes)
- Conclusion: Temperature sensor is working properly

Idle Motor:
- Applying ground to center pin and 12v to one of the outer pins (or visa versa) while the engine is running causes it to rev or die, depending on which pin is powered.
- Conclusion: Idle motor is working properly

ECU:
- Unplugging the connector with pins 9 and 11 revs idle even higher (~3200 RPMs est.)
- Shorting 9 to 11 revs at ~1600 RPM
- Conclusion: ECU is working properly

Other notes:
- Idle does not hunt; stable at ~1600 RPMs.
- We tried tweaking the timing, then tweaking the CO, and back and forth trying to get them both within range. We got it down to maybe 1300-1400 RPM, but we still had glowing headers, and leaning the mixture out any further stalled the car out.

Things I didn't get to try:
- Re-do the CPR pressure test to see it being 10% out of range is happening on a completely cold engine over 5 minutes.
- I was going to set CO as per Workshop Manual D:04:01, but that seems to require the car to already be idling properly, which it is not. Also a gas analyzer, and for some reason I couldn't find the diagnostics port, nor was it obvious how to connect a dwell meter to the frequency valve as DMCTek suggested.

The implication is that there is not a small vacuum leak (since the idle isn't hunting, and a small leak on a gasket or cracked hose wouldn't cause such a huge spike in idle, right? Unless there's a lot of them, that is), there is not a metered air leak (since the idle motor, ECU and temp sensor seem to be working), and there is no problem with the distributor advance. The spark plug wires appear to be in the correct order, as the headers glow equally (so, it's not just two plugs that are swapped).

This coming Sunday I'm going to remove the valve covers and check the valve clearances and the valve timing (pretty sure I can do that without removing the timing cover, anyway) -- unless someone has any other ideas for things I can try out.

I'd like to do a smoke test so I can be sure about the vacuum leaks, but they're far too expensive to buy and I don't want to drive the car in this condition to get it to a shop for testing. I'm tempted to make a DIY smoke machine, although I'm not sure that's wise.

Thanks again everyone!

-- Joe

[Farrar]

I'm tempted to make a DIY smoke machine, although I'm not sure that's wise.

Pull one of the manifold vacuum hoses and blow cigar smoke into it?

Farrar

[Elvis]

Great feedback, good job !

one more:
Remove the W-pipe and check the valves on the butterflies.

[jangell]

Pull one of the manifold vacuum hoses and blow cigar smoke into it?

If only I smoked. :)

I was thinking of a simple video I found on YouTube: a $30 fog machine, a cardboard box to collect the fog in, and an aquarium pump to gently feed the fog into a 't' in the vacuum line on the manifold. Seems like it should work and be reasonably inexpensive (<$50 total).

-- Joe

[jangell]

one more:
Remove the W-pipe and check the valves on the butterflies.

Cool -- I'll check that out before I take the valve covers off.

I did check the butterflies and make sure they were closed, but I didn't check the springs or valves themselves. Opening the throttles does rev the engine as you'd expect.

Thanks again!

-- Joe

[Elvis]

I'm sorry, hope you haven't started yet. please leave the W-Pipe on.

You wrote the engine idles high (how high ?) or dies when you do the idle motor test as suggested ?
This tells me if the idle motor closes all the way, it does not get enough air anymore -
no wrong air ! Mechanically everything seems fine.

The ECU is bad !!!!!

If you're sure you bridged the temp sensor with the connector on the ECU and the idle
doesn't go down - then very likely one of the output transistors is shot or one of the OP-Amps is bad.

Can you get another ECU to compare/test it before you open it ?

[jangell]

I'm sorry, hope you haven't started yet. please leave the W-Pipe on.

The car's 2.5 hours away (my condo association frowns on disassembling cars in the parking lot), so I only get to tinker with it on Sundays. So, I haven't started yet.


You wrote the engine idles high (how high ?) or dies when you do the idle motor test as suggested ?
This tells me if the idle motor closes all the way, it does not get enough air anymore -
no wrong air ! Mechanically everything seems fine.

The ECU is bad !!!!!

If you're sure you bridged the temp sensor with the connector on the ECU and the idle
doesn't go down - then very likely one of the output transistors is shot or one of the OP-Amps is bad.

Can you get another ECU to compare/test it before you open it ?

The car idles at ~1600 RPMs. Whatever else is going on, it's causing the headers to glow red after a few minutes.

I may need to check the idle motor again, just to be sure it really is closing all the way. At first it didn't die when I did it, but I thought I just didn't let it fully engage (didn't give it 12v for long enough). It worked on the second try, though. I'm tempted to remove the motor, close it and see if I can force air through it and fell it coming out the other side, just to be sure.

I tried two tests on the ECU pins; I disconnected the plug, leaving pins 9 and 11 open, and the engine idled very high (~3200 RPM). When I jumped pins 9 and 11, the idle dropped back down to ~1600 RPM.

It's also worth noting that as the engine warmed up, it seems to hold around 1600 RPM. It doesn't seek if we leave it alone. It's tough to say how consistently it's idling at that rate over time, though, as we were constantly tinkering with the CO, timing, vacuum lines and other tests to get the idle down, but it always seemed to come back to about that level. The tach readings were taken via an automotive mutlimeter with an RPM feature hooked up to the coil, as opposed to reading the car's RPM gauge.

It seems like the car thinks that 1600 RPM is a proper idle, and tries to maintain that, and we can't seem to get it to drop down to 775 RPM. The best I could get it to was ~1400 RPM by leaning the mixture out and playing with the timing, but that was on the edge of stalling.

This implies that the ECU is working, right? I don't have access to another idle ECU; I'd probably have to buy one.

Thanks again!

-- Joe

[Elvis]

Can somebody lend him an ECU ?

is there no other Delorean close to you ?

BTW - where do you live ?


and - testing the idle motor:
+12V to the center pin
GND to the outer pins ! BUT NEVER both together !

I do have a spare one and I can repair yours, but that little lake between us...called Atlantic Ocean... makes shipping a bit expensive but cheaper than a new one.

[jangell]

Can somebody lend him an ECU ?

is there no other Delorean close to you ? BTW - where do you live ?

No one I know, but there probably are. I live in Norton, MA, but the car's at my dad's house in New Milford, CT.


and - testing the idle motor:
+12V to the center pin
GND to the outer pins ! BUT NEVER both together !

That's what I did (I also did ground on the center and 12v on the other pins (which was easier with the PowerProbe), but I believe it reverses the direction of the motor). It didn't occur to me that applying power to both outer pins at once would be bad, although that's obvious in retrospect.


I do have a spare one and I can repair yours, but that little lake between us...called Atlantic Ocean... makes shipping a bit expensive but cheaper than a new one.

Yes, it does get inconvenient at times. :)

Thanks again

-- Joe

[Elvis]

It didn't occur to me that applying power to both outer pins at once would be bad, although that's obvious in retrospect.


yeah well, those motors a driven at 100Hz.
connecting both sides to GND won't make it move at all or it will move it to a center position.
Makes no sense but even worse - it's not meant to get continuously power to the
same coil. that will heat it up and burn internally.
For a quick test - touching it for a second or so - won't harm anything.


Oh wow that's near Farmington, my company is there, too.

[jangell]

connecting both sides to GND won't make it move at all or it will move it to a center position.
Makes no sense but even worse - it's not meant to get continuously power to the
same coil. that will heat it up and burn internally.
For a quick test - touching it for a second or so - won't harm anything.

That's pretty much what I thought would happen -- leave it hooked up too long and it'll fry, but a quick touch shouldn't be bad. I know JUST enough electronics to be dangerous. The same is true about engines. :)

It didn't occur to me to not constantly apply power to the motor, though (just not to apply power to both coils at once), although again in retrospect that is obvious -- it would keep trying to push and eventually fry out the motor, as you said. I was just tapping the 12v button on the PowerProbe and hearing the motor snap the valve open or closed, rather than keeping power on it.

I just checked the DMC store and saw that idle motors are $275 USD. If mine is bad, I may take you up on that offer to repair it.

If the idle motor was confirmed to be closed and the engine didn't die, would that imply a massive air leak somewhere? Since air must still be getting into the engine then, right? I'll have to test that and report back.

Thanks!

-- Joe

[Elvis]

idle ECU is bad !! not the motor !

[jangell]

idle ECU is bad !! not the motor !

I'm just thinking of other diagnostic tests. The idle ECU's job is pretty much just to control that motor, right?

The idle ECU only operates when the idle microswitch is engaged. If I were to open the throttle just a enough so that the microswitch was released and a bit of air was moving over the throttles, it should drop down from 1600 RPM to, say, 900 or 1000 RPM (or whatever corresponds to the throttles being slightly open), right? I should go up up to 1800 RPM or something like that, or else I would be getting air from somewhere else. This does assume that the idle motor is completely closed and that no air is getting in through its port.

Just a thought.

-- Joe

[dmc6960]

The idle motor will not close on its own. The ECU has to do that, and if the ECU is malfunctioning, all bets are off.

After reading about everything you have done, and considering the possibility of a bad ECU throwing off your tests...

Remove idle motor completely. Plug both ends so no air gets into engine that way. Try starting. No start? Depress throttle part way and try again. Engine should start. Let off throttle until idle is around 1000rpm. TEMPORARILY adjust stop screw there so you dont have to hold it. Push in idle switch to cut-off vacuum advance to distributor. Slightly lower throttle some more to get it around 800rpm. Perfect, now you have an idle you can safely adjust your ignition timing (first!) and then fuel mixture (second!). THIS SHOULD STOP THE GLOWING HEADERS! I suspect if your fighting a malfunctioning ECU and you've tried adjusting the timing AND the fueling to compensate, that would be causing the glowing headers. A bad idle ECU alone would NOT do this on a properly tuned engine.

Once the headers stop glowing, obtain a temporary idle ECU, set all throttle stops back to normal on the engine, and reinstall idle motor. Test, find real fault, repair/replace, done.

[jangell]

The idle motor will not close on its own. The ECU has to do that, and if the ECU is malfunctioning, all bets are off.

Right, sorry, I was planning on unplugging the ECU connection to the idle motor and applying 12v to the appropriate pin to close the motor. Wether it would stay closed and not slip open again is another story.

Plan B was to do what you suggest, although you mentioned a bunch of stuff I didn't think of (temporarily adjusting the stop screw, pushing in the idle switch to cut off the vacuum advance, etc).

You are exactly correct that I've been adjusting timing and fueling to compensate for the bad idle, and failing to get anywhere.

I'll give this a shot on Sunday. Thanks!

-- Joe

[Elvis]

Leave the motor in there and do what you thought. I know other people who unplugged the idle motor in a sweet spot where it idled nicely and never plugged it back in.
He called himself an EE...


The idle micro switch does not turn the idle system off.
instead it sets the speed above 800rpm - more like 1200rpm or so.

the brass screws also work very nicely :-)

[Bitsyncmaster]

No engine will have hunting issues at 1600 RPM. At that speed the idle motor should be fully closed and not moving from there.

You should unplug the idle motor when the car is idling at that RPM, then shut off the engine. Then you pull the idle motor out and look at the valve and verify it is fully closed. If closed, you idle problem is elsewhere, if not closed you probably have a bad idle ECU.

Never adjust the mixture to fix an idle problem. You connect the dwell meter on the FV valve pin or use the orange wire on the two pin connector near the diagnostic connector.

[dmc4087]

This is my smoke tester kit

http://i19.photobucket.com/albums/b160/88mph/2-21.jpg

http://i19.photobucket.com/albums/b160/88mph/1-24.jpg

http://i19.photobucket.com/albums/b160/88mph/3-20.jpg

I place an oily rag into a small glass jamjar - I ignite this, let it burn for a bit then place it inside the plastic container and quickly close the two halves - seal the joint with duct tape.

The lack of oxygen puts the flames out but plenty of smoke will still come out the top tube (connect this to the back of the intake manifold)

Get an assistant to blow through the bottom tube.

Be sure to tape up the intake, then watch for the leaks!

[jangell]

I'm afraid I've been fighting starter issues the last couple of weekends and haven't had a chance to do much else (like test the idle ECU):

When I turn the key, the starter solenoid engages, but it often doesn't turn the engine. If you turn the key a few times it'll eventually start turning. It's sort of like it's "stuck". This is with a fully charged battery jumped to a second fully charged battery hooked up to a battery charger set to the 100 amp "jump start" mode, so I'm pretty sure I have enough juice to run the starter. I started clicking the key quickly between off and run until it would start to crank. My starter was on the way out anyway, so I wasn't worried about damaging it further.

Recently I got another starter to replace this one. Installed it, and was surprised to find that I had the same problem. I Removed it (PITA with the Spec I and probably other after-market exhausts, since you have to remove the headers) and bench tested it, and it worked perfectly. I then connected it to the car's electrical system (but not mounted to the flywheel; I used a jumper cable for ground), and it again worked perfectly.

But when mounted to the bell housing, the solenoid engages but the engine usually doesn't turn. Turn the key a few times and it will turn the engine. More often than not (say, 9 out of 10 times), the engine will simply not turn. I crawled under the car while someone turned the key and couldn't hear the starter trying to turn, but I"m not sure if I should be able to hear anything anyway.

Has anyone ever experienced this sort of thing before? I don't think this was happening before I put in the new cams.

I'm trying to think of what other tests I can do. I was considering a bad ground to the stater's mounting flange, but that doesn't seem likely, especially since it actually does turn sometimes. I was also wondering if there was some sort of extra resistance on the flywheel that was keeping it from turning, but I'm not sure that seems right either, since when it does turn it seems to be fine.


The one other non-starter-related test I was able to do was a smoke test using the fog machine rig I mentioned earlier. This worked, but the fog was fairly faint and whispy. Still, I did not see any leaks, just fog coming up from the venturi and out of the oil filler air box connection (since I didn't have the air box on).

Thanks again!

-- Joe

[Ron]

Did you replace the starter and solenoid?
When it does crank over, is it at a normal speed?
Try running a cable directly from battery (-) to the starter case.
Do you have a low VIN (they need a relay socket wiring update)?

[Bitsyncmaster]

Sounds like you have a bad connection. As Ron suggested, use a jumper cable to check for a bad ground. Have you looked at the crimps on the ends of the large wires. My battery + wire had a very poor crimp by a PO on the battery end and the factory end was pretty poor also.

[jangell]

Did you replace the starter and solenoid?

Yup, the whole thing. I'm actually testing out a new starter from britishstarters.com. A friend of mine has worked with them before for other cars. They take a modern high-torque Japanese starter and design a mounting plate for your car. I sent them my old starter so they could machine the plate, and then sent me both my original and the new one back. Like with some Eagle Premiere starters, I connected the ballast resistor wire to the solenoid wire, as there is no provision for the ballast resistor's bullet connector on this starter. Since they have the mounting plate design now, they can easily make new plates for other DeLorean owners. The starters are in the mid-$200s (about the same as a stock DMC starter). They haven't even asked me to pay for it until I know that it works, and had no problem with me mailing back the mounting plate for a couple of new holes to work around the constraints imposed of the engine, headers and engine cradle.


When it does crank over, is it at a normal speed?

I'm not entirely sure, as I'm not sure what "normal speed" is. The old starter seemed to quickly lose speed after a couple of revolutions, like it was very quickly draining the battery. I haven't thoroughly tested the new one yet, since I was more interested in figuring out why the starter isn't spinning the engine at all vs. how fast it was spinning it.

I also haven't bench tested the old one, just the new one.


Try running a cable directly from battery (-) to the starter case.

I'll give that a go next time I'm near my car. I didn't think to try that until I was on the way home last night.


Do you have a low VIN (they need a relay socket wiring update)?

I do, VIN 767. When I got the car about 10 years ago, it didn't have any upgrades done (melted fan fail relay and everything). I've since done that update. In fact, at one point I added my own relay that provided direct power from the main battery post in the engine bay to the starter solenoid when the key was turned. This mod was removed when I replaced the main engine harness this winter. The solenoid appears to have full power, though, in that I can hear it engaging every time I turn the key with both starters.

Any idea how many amps the solenoid should draw? I'd like to use an amp meter to ensure that it is correct. Actually, I guess I can figure that out by hooking the solenoid directly up to a battery instead of to the car's wiring, although if I can hear it engaging I guess it is working properly.

Thanks!

-- Joe

[jangell]

Sounds like you have a bad connection. As Ron suggested, use a jumper cable to check for a bad ground. Have you looked at the crimps on the ends of the large wires. My battery + wire had a very poor crimp by a PO on the battery end and the factory end was pretty poor also.

I had to replace the wire between the alternator and starter with a longer one due to the configuration of the new after-market starter, so I know that one's good. The crimp on the other cable (the heavy one that goes to the batter and does not look easy to replace) looks good, in that it is very tightly wrapped around the wires. I'm not sure if it's soldered on. I'd be willing to replace the cable, but it looks like it sits between the frame and the body, and is not easy to do.

I didn't take a close look at the terminals on the battery end. I'll check that out next time I'm at my car (either this or next weekend). I'll definitely use a jumper cable to test for a bad ground next time too.

When I tested the starter motor by connecting it to the car's wiring but not mounting it in the car, I used a jumper cable connected between the stater's mounting flange and the back of the engine near the oil pan, and it seemed to work fine. However, I did not run the cable to where the starter mounts on the car, so I'll check that next time.

Thanks!

-- Joe

[Bitsyncmaster]

Any idea how many amps the solenoid should draw? I'd like to use an amp meter to ensure that it is correct. Actually, I guess I can figure that out by hooking the solenoid directly up to a battery instead of to the car's wiring, although if I can hear it engaging I guess it is working properly.

Thanks!

-- Joe

The solenoids on "chevy" starters use a two coil setup. It uses a high power coil to pull the solenoid in and then a lower power coil to hold it in. I think the low power current is about 10 amps so I would guess the high power coil to be about 20 amps.

[jangell]

The solenoids on "chevy" starters use a two coil setup. It uses a high power coil to pull the solenoid in and then a lower power coil to hold it in. I think the low power current is about 10 amps so I would guess the high power coil to be about 20 amps.

Either of those would blow the fuse on my 10 amp multimeter. :)

Thanks

-- Joe

[jangell]

Ok, here's the latest news:

Got my starter issue resolved. After much tinkering, I re-added my starter solenoid bypass (a relay that provides direct battery power to the solenoid), and it worked. I then re-checked the start inhibit relay and found that, contrary to my previous assertion, the starter fix was NOT installed on my car. So, that explains a lot. My relay in the engine bay does basically the same thing in a more round-about manner. The new starter works greats and cranks much more consistently and at lower battery levels than the stock one, once I shimmed it out so it didn't scrape against the flywheel once the engine was running.*

Now I'm back to the high idle issue again. I reset the fuel distributor's CO to a useful default by pulling an injector, running the fuel pump and turning the CO screw until the injector just slightly dripped, and then turned it back unit it stopped.

I took off the idle motor, and found exactly zero effect in how the car operated -- it started right up with the motor out of the car and the lines plugged. I then completely blocked off the air coming into the Venturi, and the car immediately died (no sputtering or anything like that - it just went off). The idea here is that if there was a lot of other air coming in, the car still would have tried run, rather than just shutting off like that.*

I tried backing the curb idle screw all the way out, and could not starve the engine of air -- the Venturi still always stayed a little open. I made sure the idle switch screw wasn't keeping the throttle out as well.*

I tried to find the diagnostic port so I could hook a dwell meter up to it, but I simply couldn't locate it. I get the impression that it should be near the CPR, but there's nothing there on my car.*I'll attach a picture of the relevant area. Any idea where it might have run off to?

Last question of the day: I was under the impression that if it he distributor vacuum advance was disconnected, the distributor timing would be fixed. However, it seems that the distributor timing is changing as the RPMs change (meaning, as I adjust the CO), which doesn't make any sense unless something else is advancing the distributor, or I'm doing something very wrong.

Thanks again for the assistance!

-- Joe

[ramblinmike]

Ok, here's the latest news:

Got my starter issue resolved. After much tinkering, I re-added my starter solenoid bypass (a relay that provides direct battery power to the solenoid), and it worked. I then re-checked the start inhibit relay and found that, contrary to my previous assertion, the starter fix was NOT installed on my car. So, that explains a lot. My relay in the engine bay does basically the same thing in a more round-about manner. The new starter works greats and cranks much more consistently and at lower battery levels than the stock one, once I shimmed it out so it didn't scrape against the flywheel once the engine was running.*

Now I'm back to the high idle issue again. I reset the fuel distributor's CO to a useful default by pulling an injector, running the fuel pump and turning the CO screw until the injector just slightly dripped, and then turned it back unit it stopped.

I took off the idle motor, and found exactly zero effect in how the car operated -- it started right up with the motor out of the car and the lines plugged. I then completely blocked off the air coming into the Venturi, and the car immediately died (no sputtering or anything like that - it just went off). The idea here is that if there was a lot of other air coming in, the car still would have tried run, rather than just shutting off like that.*

I tried backing the curb idle screw all the way out, and could not starve the engine of air -- the Venturi still always stayed a little open. I made sure the idle switch screw wasn't keeping the throttle out as well.*

I tried to find the diagnostic port so I could hook a dwell meter up to it, but I simply couldn't locate it. I get the impression that it should be near the CPR, but there's nothing there on my car.*I'll attach a picture of the relevant area. Any idea where it might have run off to?

Last question of the day: I was under the impression that if it he distributor vacuum advance was disconnected, the distributor timing would be fixed. However, it seems that the distributor timing is changing as the RPMs change (meaning, as I adjust the CO), which doesn't make any sense unless something else is advancing the distributor, or I'm doing something very wrong.

Thanks again for the assistance!

-- Joe

The ignition timing will advance as the engine RPM increases. That is normal. There are weights in the distributor that do this on purpose.

[jangell]

The ignition timing will advance as the engine RPM increases. That is normal. There are weights in the distributor that do this on purpose.

Ah, that explains a lot. So as I bring the idle down by adjusting the CO, I need to bring the distributor timing back up to compensate for the weights.

I guess this also explains why I saw a post about tacking the distributor so it can't advance when using Megasquirt to control spark.

Thanks!

-- Joe

Attached is the picture of my engine bay, where I think the diagnostic port should be. A check of the Parts Manual suggests that it simply isn't in my car at all. Luckily, it looks like I can just hook up to the orange wire on the Lambda plug meant for the diagnostic port and use that for the dwell reading. I'll give that a try and see what I get.

8779

-- Joe

[jangell]

One more quick update: while fiddling with the CO and distributor timing while waiting for the engine to warm up so we could check the dwell, we suddenly noticed the right cat (DPI SPEC 1 exhaust) glowing red. The headers are not glowing, and the left cat is not glowing -- it's only the right side. Very strange.

Thanks again

-- Joe

[deloumis]

One more quick update: while fiddling with the CO and distributor timing while waiting for the engine to warm up so we could check the dwell, we suddenly noticed the right cat (DPI SPEC 1 exhaust) glowing red. The headers are not glowing, and the left cat is not glowing -- it's only the right side. Very strange.

-- Joe

Glowing cat usually means either timing is off, or running rich.

[jangell]

Finally figured out the problem: The throttles were indeed open, as bitsyncmaster and Elvis had suggested. With the W pipe off they looked like they were pretty much closed, but when we took the throttles out of the car it was clear that light was shining right though them. I have no real intuition for how closed they were supposed to be, but it was clear that they were too open when the throttle was out of the car. We'd adjusted the curb idle screw, but to no effect.

It turns out the throttle arm (the vertical piece of metal that holds the idle screws) was itself bent, and was twisting just enough to keep the throttles from closing properly. This was letting enough air through to cause the engine to rev at double what it should.

I replaced the throttle arm, and everything worked perfectly. I was finally able to take the car for a drive on Sunday!

Now I'm trying to figure out a weird issue where shifting from P/N to R/D will cause the RPMs to drop and sometimes stall, although if it doesn't stall it will stabilize at ~900 RPM. When shifting from R/D back into P/N, the car will rev up to 1500 RPM before settling back down a few seconds later, at which point it the idle will hunt (even when warm).

It'll be early April before I can tinker with it again, but at least it's running and drivable. I've learned a whole lot more about how engines work now. Thanks to everyone for their assistance!

-- Joe

[Bitsyncmaster]

Sounds like you have a sticky idle motor. It should not take seconds to stabilize the idle RPM. Does it do better when the engine is cold? The idle speed should be 775 RPM and not 900 RPM.

[jangell]

Sounds like you have a sticky idle motor. It should not take seconds to stabilize the idle RPM. Does it do better when the engine is cold? The idle speed should be 775 RPM and not 900 RPM.

The idle motor seemed to soundly snap open and closed when tested with a PowerProbe, but I didn't do any thorough tests on it as yet.

We were excited to actually take the car for a drive, so we didn't let it cool down again to test it out. I'll have to try it next time and see if the idle is better when it is cold vs hot. I will note that I didn't have this issue when I took the car apart a year and a half ago.

The high idle is much better than it was before. My friend has access to a CO meter, which we're going to use in combination with a dwell meter to properly adjust it. I assume it makes sense to get that in range first? Or does it make more sense to diagnose the idle motor first?

Thanks!

-- Joe

[Bitsyncmaster]

Do your engine adjustments first. Mixture has a small effect on idle. Engine timing also affects idle. Vacuum leaks also have major affects.

My car had a high idle only after it was warmed up and no loads (AC or headlights) on. It turned out to be bad springs on the deceleration valves. That let air pass the throttle plates.

[Elvis]

Hey those are good news :-)

Elvis & 6548

[jangell]

Do your engine adjustments first. Mixture has a small effect on idle. Engine timing also affects idle. Vacuum leaks also have major affects.

Ok, will do. The engine timing is now set at 13 degrees on idle, and I'm fairly certain that I don't have any vacuum leaks (spent a lot of time looking into that before finding the throttle arm issue).


My car had a high idle only after it was warmed up and no loads (AC or headlights) on. It turned out to be bad springs on the deceleration valves. That let air pass the throttle plates.

Ah -- I'll make sure to check to see what happens at different engine temperatures.

Thanks!

-- Joe