New Owner: Hesitation, missing, strong exhaust

[smcguiga]

I've had my Delorean for a few months now and all of a sudden the engine started to run a little rough. A few months ago I was trying to tackle the strong exhaust and was able to set my adjusting the mixture using a dwell meter as described on some posts here. (DMCFL had it running too rich). Everything ran fine for a few months (still strong smell but acceleration was better) and I've been running non-ethanol gas with some B12chemtool additive and that definitely made an improvement. However, just recently without any change, it started to run rough and sounds like maybe one of the plugs isn't firing. Acceleration sounds like a motorcycle. I can place my hand over the exhaust and it isn't smooth. Today I replaced the spark plugs with new ones from DPI (old ones were NGK and a few were very black ) but that made no change. My next step was to change the plug wires, then move to the distributor cap. I also tried screwing in the three brass screws as they were not completed closed and that didn't seem to make any difference at all. I read numerous posts on here where it was recommended that these be closed. I've recently received a relay upgrade kit from DMCH and was going to go ahead and swap those out. I'm interested in the SS RPM relay from Dave and might purchase that soon.

On another note my auto transmission has been having delayed shifting and occasional down shifting at random times but that is another issue that I will address soon. I'll likely first try changing the oil and filter and if that doesn't give me improvements I'll remove the governor and send it in for a rebuild.

Thanks for any assistance!

--Steven

[Bitsyncmaster]

You will need to adjust the mixture again after doing all that work. Remember to do the adjustment on a warmed up engine.

[David T]

Sounds like a sticking fuel plunger and/or dirty fuel injectors. Do you hear the frequency valve buzzing? As for the automatic trans, you should do a service on it and repair or replace the shift computer.

[Jonathan]

Hi Steven,

It sounds like you have a few different issues that can be, or should be, tackled separately.

First, the easy one (to comment on, not fix, necessarily) is the issue you are having with the auto trans. Yes, sounds very likely to be your shift computer causing those problems. If you describe your car doing things regarding the transmission as "random" that's generally going to fall into the category of needing to rebuild your shift computer governor.

You have noticed a strong (smelling) exhaust and saw one or more of your spark plugs as being black when you replaced them. So, your car has been running rich, that much seems obvious. What might be less obvious is why.

What can be causing there to be too much fuel reaching the cylinders?
- fuel injectors which have failed in some way and are letting fuel pour into the cylinder that isn't supposed to be. This is also where the stuck fuel distributor plunger problem would show up.
- the Lambda ECU system deciding to put too much fuel into the cylinders, rightly or wrongly.

If you take your injectors out and do the jar testing method to see how the flow (pattern) is, this will tell you a lot more about whether this is your problem.

If the injectors aren't the problem, and the Lambda ECU system is "purposely" putting too much fuel into the cylinders, there can be a few reasons why it would choose to do such a thing.
- It could be that the CO mixture is set too rich. This sounds like any easy place to start, and it is, but unfortunately it's the last thing you do to fix things, not the first. You likely need to circle back to this as Dave M. mentioned, but get all the other stuff sorted out first.
- You could have one or more control switches tricking the Lambda fuel system into a mode that is enriching the fuel mixture. It could be the fuel enrichment microswitch at the throttle spool that's not working correctly. Could be a bad oxygen sensor that's fooling the Lambda ECU. Could be the thermistor and/or its connector convincing the Lambda ECU the engine is not warmed up when it really is, and keeping it in some enriched fuel mixture mode.

You have swapped out a lot of parts, and while that can cause problems trying to pinpoint a problem, it doesn't make it that much more difficult. What it can help you do is force you to ensure everything is back to its intended design position and then start from there. This is especially true if you are new to your car.

This includes:
- those three brass screws you mentioned. Manual calls for them to be dialed in all the way. Make it so.
- confirm your throttle spool adjustment stops are allowing the butterfly valves assembly to come back to its rest position properly when the accelerator is not being pressed and the idle microswitch is being engaged at the same time. Confirm also it comes off that rest position when the accelerator is pressed.
- if you cannot confirm the fuel enrichment microswitch (and kickdown microswitch for the automatic trans in the same location) is working properly, then unplug it at the plastic connector.
- double check all six of your spark plug wires are well connected to the top of the spark plugs (and the routing is correct from the distributor to each cylinder. Confirm this routing for the fuel lines as well as the ignition wires).
- confirm the routing of all vacuum lines, fuel lines and fuel and idle system electrical connections.

Basically, to ensure you get resolved whatever it is that's causing your problems, you need to go back and start from as far back as necessary until you reach a point where you know for certain things are as they should be.

If you said you've owned this car for ten years and only just the other day did it start acting up, I'd say you wouldn't have to go very far back. Since the car is new to you though, you may need to go back quite a ways and even double check a few basics like ignition coil and ballast resistor wiring, fuse and relay wiring or condition, fuel line routing or accumulator and filter condition, etc.

You may have had the car at DMCFL before you got it, but depending on what they were asked to work on, and paid to work on, there still could be some fundamental problem that was missed and has yet to be sorted out. That's not a given of course, but not something you can definitively rule out either.

[smcguiga]

Thanks so much for the information! Each problem is an opportunity to learn more about this car (trying to stay positive here) :)

The strange transmission shifting seemed to start when I would drive it on a cold morning then it would clear up after warming up. I do have a little bit of a transmission fluid leak but every time I've checked it, it still shows within range. From what I have read about the upgrade/rebuild, it seems to be well worth it.

I changed out the relays and I just now rechecked the dwell and adjusted the mixture slightly to get it back to normal (~40 at 750rpm and pressing WOT pushes it to 50). At Cold startup the dwell sat still, then started to bounce between 50 and 70, so I dialed it down a bit to where it was bouncing between ~35 and ~55 or so and kept putting my finger over the hole to double check (FV is buzzing fine BTW).

I'm starting to wonder if the previous owner drill out the CAT. Wouldn't the exhaust be worse without a catalytic converter? Wasn't sure if I should get a new one or try a "Test pipe" to see if it makes any difference...anyone that has replaced or removed the cat notice a change in exhaust smell?

I haven't replaced the wires and cap yet as I believe I'm going to have to remove the intake to get to everything. I've tried to examine all of the vacuum lines and can't detect any leaks from what I can see. I've purchase new seals, etc for the intake so I'll likely work on removing this and replace all vacuum lines and test the injectors and then install the new cap, rotor, and wires. I have new injector seals on the way as well as have new copper washers for the fuel lines just in case I had to remove them. I always like to buy a few extra things to have on hand in case I do need to go further with a job that way I don't have to wait another week to get something in. I figure at some point I'll use them anyway.

Regarding:
- confirm your throttle spool adjustment stops are allowing the butterfly valves assembly to come back to its rest position properly when the accelerator is not being pressed and the idle microswitch is being engaged at the same time. Confirm also it comes off that rest position when the accelerator is pressed.
- if you cannot confirm the fuel enrichment microswitch (and kickdown microswitch for the automatic trans in the same location) is working properly, then unplug it at the plastic connector.

The idle micro switch is engaging/working just fine, need more education for the fuel enrichment and kickdown switch. :)

I recorded a video here: https://www.youtube.com/watch?v=SqApzamW1J4
Does it sound "normal" to you? Doesn't feel or sound as smooth as it should.

Thanks again

[Bitsyncmaster]

My CAT is gutted and I don't notice any difference in the exhaust smell.

[Jonathan]

Regarding:
- confirm your throttle spool adjustment stops are allowing the butterfly valves assembly to come back to its rest position properly when the accelerator is not being pressed and the idle microswitch is being engaged at the same time. Confirm also it comes off that rest position when the accelerator is pressed.
- if you cannot confirm the fuel enrichment microswitch (and kickdown microswitch for the automatic trans in the same location) is working properly, then unplug it at the plastic connector.

The idle micro switch is engaging/working just fine, need more education for the fuel enrichment and kickdown switch. :)

I recorded a video here: https://www.youtube.com/watch?v=SqApzamW1J4
Does it sound "normal" to you? Doesn't feel or sound as smooth as it should.

Thanks again

You're welcome.

On the video, hard to say with only the one view and not seeing what the tach is doing during this, among other things, but that doesn't seem to be idling too badly at all. "Smooth" is a pretty relative term with these cars. Shuddering is one thing it doesn't look to be doing. They'll do that at times when hunting for idle, or if the fuel mixture is out of whack.

The engines are also something called "odd fired" which probably means a bunch of things, but one thing it will mean to you or I putting your hand (carefully) in front of either exhaust pipe tip is that the feeling will be that it "pulses." The "odd" means something other than "strange" but it will feel unusual if encountering that for the first time.

Now, one other thing from your video, and this is possibly nothing more than noticing a little uniqueness in your engine bay that won't matter, but thought I'd mention it anyway and perhaps Dave or someone else can tell me if it's a problem.

The top half of your cold start valve looks to be installed 180 degrees rotated off from where it normally would be.

I can see the lower half still has the hose connections facing the way they normally would, but the connector on top (specifically the blue coloured electrical connector) caught my eye as it looks like it's pointing the other way. I have not taken one of these apart, so can't say for certain if the insides are symmetrical enough that installing it 180 degrees off is a problem or it isn't. Sort of how the old school light bulbs wouldn't care, but the polarity of the LEDs would lead to this not working. Could explain excess fuel getting into the engine if indeed things were going past the cold start valve that weren't supposed to be.

Those two microswitches are the ones kind of hidden by the W pipe and just up in front of the throttle spool (where your hand is in the video). Basically, when you floor it, or try to get out and around someone, it does two things. The throttle spool by way of physically turning the entire way will bump up against a metal flap and engage the switches while floored. The lower switch (with the flap) is the fuel enrichment switch and adds some extra fuel to the mixture) and the upper switch (without the flap) tells the auto trans to kick down to a lower gear for passing.

If these are not working, and stuck closed would be the worst position for them, it would cause your trans to do funny things (probably not the stuff you described, but other funny stuff), and it would also keep feeding your engine more fuel than it needs (i.e. keeping it enriched). Neither is ideal. The manual trans only has the lower switch. If you know one only is good, on the auto trans, it'd be better to have the kickdown one working.

You can unplug them at that white and black connector on top of the W pipe for the time being if you're unsure and want to rule them out. They really only get used when you floor it, which granted, is not likely very often.

[smcguiga]

I recording another video from startup inside the cabin and around the engine a bit more. Strangely enough, the engine is running smooth now!?!!! What in the world?!? Its not as apparent in the video, but when revving the engine its more smooth than it was earlier and the Exhaust isn't pulsing like it was doing before when I put my hand in front of the pipe. As stated originally, when i received the car a few months ago and got it home and was checking the dwell I had to lean the mixture 1/4 of a turn from when it was set at DMCFL, so maybe I'm still dealing with some carbon deposits on the valves or something. Strange how it can be different from crank to crank.

The microswitches you were referring to is what I have read as the wide open throttle switch. I didn't realize it was two switches on top of each other. Both are engaging properly when pressing. You should be able to see the blue connector better.

https://www.youtube.com/watch?v=nwJhyypbubM

Now if I can just figure out why the exhaust stinks so bad...my clothes wreak! :(

Thanks!

--Steven

[Jonathan]

It's a, uh, little known fact that these cars can just magically fix themselves sometimes.

Or at least it seems that way!

It could be deposit related, sure. Could be a few other things too, like trying the engine more frequently and burning off gas that was left in there but not replacing it right yet with new, excess gas. Somethings on the car get better when it's warm too. Seals for one, same for solder joints. You'll notice the auto trans governor fails differently when warm versus cold.

It is St. Patrick's Day though! Maybe you had a lucky Leprechaun come into the garage while you were in the house and fix it for you??!!

Keep an eye on it and just keep observing what it's doing. Getting familiar with it, in the good and the bad, is about the best trouble shooting training you can give yourself.

[Trstno1]

Boy, based on the video I'd say the engine is running pretty well. I too am in the pursuit of a perfectly running engine. I have also noticed the difference in running from start to start.... It gets a little frustrating to say the least. Definitely let us know the tweaks you are making and if it helps or hinders.

[David T]

Boy, based on the video I'd say the engine is running pretty well. I too am in the pursuit of a perfectly running engine. I have also noticed the difference in running from start to start.... It gets a little frustrating to say the least. Definitely let us know the tweaks you are making and if it helps or hinders.

If the motor was running very rich and now you leaned it out, it can take a while for the O2 sensor to burn off all of that fuel and start working again. That may be why it is running better or it may be a bad/dirty electrical connection and it is working better now that you touched something. If it is OK leave it alone and see if it stays OK. As for the shift computer, it is not unusual for the symptoms to be temperature related. Usually because of cold solder joints. To get the motor to run "perfectly" you have to start with balancing each cylinder to within 5% with a compression test if you can.

[RamblinDMC]

My car used to run good and bad intermittently. Turned out to be a faulty new combo fuel pump/sending unit. Replaced it with an OEM style Bosch pump and solved all of the issues. It has ran fantastic since.

Sent from my XT1049 using Tapatalk

[refugeefromcalif]

Hey Steven, Nice meeting up with you yesterday. It's Great having another local owner around town.

40929 40930 40931

Let us know how your diagnostics go.

George

(BTW, Do you want to swap seats)... ;-)

[smcguiga]

I thought one of my plugs wasn't firing since removing the cable didn't seem to make a difference so I replaced the plug wire on that one and still no difference (plugs have already been replaced). I replaced the o2 sensor yesterday and the old was was very black, but STILL no difference. I just now started it up and noticed that when I unplug the FV bulkhead connector, the engine doesn't change at all. When plugged in I can hear the FV buzzing, but unplugged makes no difference. Thoughts?

--Steven

[Bitsyncmaster]

I thought one of my plugs wasn't firing since removing the cable didn't seem to make a difference so I replaced the plug wire on that one and still no difference (plugs have already been replaced). I replaced the o2 sensor yesterday and the old was was very black, but STILL no difference. I just now started it up and noticed that when I unplug the FV bulkhead connector, the engine doesn't change at all. When plugged in I can hear the FV buzzing, but unplugged makes no difference. Thoughts?

--Steven

Have you set your dwell? Another possibility is your fuel return line is plugged. A fuel pressure test would show a plugged return line. I'm not sure what the unpowered FV would do but guess the mixture should change.

[smcguiga]

Have you set your dwell? Another possibility is your fuel return line is plugged. A fuel pressure test would show a plugged return line. I'm not sure what the unpowered FV would do but guess the mixture should change.

I checked the other day not fully warmed up and it was right at 45. I haven't checked it fully warmed and watching the meter cycle since last setting it a month ago. I guess at this point I'm just going to have to test all injectors and then pull the fuel mixture unit and go ahead and change out the rest of my wires, distributor cap, and rotor. Trying to route the plug wires around the fuel lines isn't an easy task. Any reason to go ahead and remove the intake manifold as well? It looks like once the mixture unit is out I can easily get to everything I need to get to. It sure is fun trying to determine fuel vs ignition issue. I feel like permanently installing gauges and meters all over the place to be able to constantly monitor it. LOL!

Where are the best places to tap into the fuel lines to test the pressure? Any recommendations on a meter to purchase or just borrow one from Autozone?

[smcguiga]

I checked the other day not fully warmed up and it was right at 45. I haven't checked it fully warmed and watching the meter cycle since last setting it a month ago. I guess at this point I'm just going to have to test all injectors and then pull the fuel mixture unit and go ahead and change out the rest of my wires, distributor cap, and rotor. Trying to route the plug wires around the fuel lines isn't an easy task. Any reason to go ahead and remove the intake manifold as well? It looks like once the mixture unit is out I can easily get to everything I need to get to. It sure is fun trying to determine fuel vs ignition issue. I feel like permanently installing gauges and meters all over the place to be able to constantly monitor it. LOL!

Where are the best places to tap into the fuel lines to test the pressure? Any recommendations on a meter to purchase or just borrow one from Autozone?

Well I made an incorrect assumption based on results where the bulk head connector I was unplugging had to do with the FV, but according to diagrams (specifically PJ Gray's booklet) the connector I was unplugged which made the FV stop buzzing is shown as the O2 sensor. Would this be the same as unplugged the o2 sensor from behind the rear drivers tire? I'm trying to understand the relationship between the FV and o2 sensor since unplugging this connect silences the FV.

--Steven

[Bitsyncmaster]

I made my own fuel pressure gauge with some old banjo fittings and a fuel rated shutoff valve. But for $100 you can probably buy one the same as mine. The pressure gauge connects to the center banjo on the FD. Then the shutoff valve and other hose goes to the line from the center banjo. With my gauge I remove that one hose and install my gauge hoses to replace it.

You close the valve and jumper the RPM relay to read primary pressure (75 psi). You open the valve and idle the engine to read control pressure (20 psi cold to 50 psi warm).

[smcguiga]

Well now I know why unplugging that spark plug wire didn't make a difference. I have a bad injector! :(
Getting the driver's side injector closest to the firewall out was quite difficult with the copper pipe in the way. Luckily I was able to move it enough to slip the line from underneath it after taking the line loose from the FD. Of course now I need new copper washers.

I did swap injectors to make sure the problem followed the injector. And of course, I haven't ordered any injectors to have on hand for "just in case", so now the waiting game begins until I can get the new injector in.

I created a video performing the test. Old glass Spice Jars work great for this!

https://www.youtube.com/watch?v=h-SY-rodtus


--Steven

[DMCVegas]

Old glass Spice Jars work great for this!

That's even better than baby food jars! Nice!

[OverlandMan]

Well now I know why unplugging that spark plug wire didn't make a difference. I have a bad injector! :(
Getting the driver's side injector closest to the firewall out was quite difficult with the copper pipe in the way. Luckily I was able to move it enough to slip the line from underneath it after taking the line loose from the FD. Of course now I need new copper washers.

I did swap injectors to make sure the problem followed the injector. And of course, I haven't ordered any injectors to have on hand for "just in case", so now the waiting game begins until I can get the new injector in.

I created a video performing the test. Old glass Spice Jars work great for this!

https://www.youtube.com/watch?v=h-SY-rodtus


--Steven

I've been using Diet Dr Pepper 12 oz plastic bottles.

Good to see you've found a bad injector that would be your likely running rough culprit.

It's more frustrating when all 6 of your injectors are flowing acceptable patterns and same volumes and the thing still runs rough. That's where I'm at right now.

[David T]

I've been using Diet Dr Pepper 12 oz plastic bottles.

Good to see you've found a bad injector that would be your likely running rough culprit.

It's more frustrating when all 6 of your injectors are flowing acceptable patterns and same volumes and the thing still runs rough. That's where I'm at right now.

It is worth having the injector cleaned before replacing it. They can be cleaned up often. Might as well send the whole set out. All the vendors offer that service and if any won't work they can be replaced. Might also need new injector seals, definitely replace the copper sealing washers.

[smcguiga]

It is worth having the injector cleaned before replacing it. They can be cleaned up often. Might as well send the whole set out. All the vendors offer that service and if any won't work they can be replaced. Might also need new injector seals, definitely replace the copper sealing washers.

I went ahead and ordered one and it should arrive today. I have new seals and copper washers as well, as I was planning to remove the FD to replace the distributor cap, wires, and vacuum lines before I found the bad injector. I'm hoping the new injector will resolve my issues so I can hold off on the other work for a while. Is there a torque setting for the fuel lines?

--Steven

[Jonathan]

I went ahead and ordered one and it should arrive today. I have new seals and copper washers as well, as I was planning to remove the FD to replace the distributor cap, wires, and vacuum lines before I found the bad injector. I'm hoping the new injector will resolve my issues so I can hold off on the other work for a while. Is there a torque setting for the fuel lines?

--Steven

See attachment here for removing the intake manifold.

http://dmctalk.org/showthread.php?429-How-to-Removing-intake-manifold

Torque values mentioned on page 9 of 16 are 7 ft lb for the 12 mm head fittings and 14 ft lb for the 17 mm and 19 mm fittings.

If one or more connections don't seal properly once you get it all back together, you can back the fitting off slightly and then retorque it. This will try and have the softer copper material fill in around the imperfection causing the leak. Conversely, you can torque it a little more. 8 ft lb is probably fine, maybe more. If you snap the hollow bolt, you got it too tight.

[smcguiga]

Ok, so I got the new injector in and that definitely resolved the "missing" that I was having. I checked the dwell again and had to make a small adjustment and its running nice and smooth.

I decided to go under the car and take care of my oil leaks and change out the accumulator. Apparently the accumulator had been replaced around 2012 with one from specialTauto, but check out the junk that came out of it! (This came out of the rear, clamped hose line)
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Getting the new accumulator installed from DMCH was quite a task as it was a bit bigger. Anyway, no leaks here so I moved to changing out the leaky Oil sensor (drivers side) and went ahead and installed the new updated Oil sending unit (passenger side). I noticed that the threads were tapered and it got really tight only after a few turns. This is about as far as I could get it in (about 1/4 inch) without feeling like I was going to break something. Does this look normal for this longer sending unit? Its working great, no longer bouncing around like crazy! :)
41170

Lastly, I took care of my transmission leak by installing a new gasket from DPI and installing a new filter while I was in there (Thanks Michael). The old filter bolts weren't tight at all and I tired to put them back on about as tight as they were to get off, maybe a little more. The old filter had a good bit of gunk on the magnet, more than I would suspect for only 11,500 miles. Regarding the pan bolts, I wasn't sure how *tight* the bolts are supposed to be as they never really got very tight but I stopped once the gasket started to bulge/squish out a little. The old gasket has washers inside the holes so it prevented the gasket from crushing and the bolts were much tighter to remove. I couldn't get them anywhere near this tight putting them back in. I tried to use my torque wrench on 3 ft lbs and never got a click. Any insight here?

In trying to get the new oil sensor unit in, the heat shield under the catalytic converter just shredded. I had a mask on and went ahead and just removed it, trying to be as careful as possible with the asbestos. Is a heat shield here even needed?

Anyway, long day...learned a lot....new injector, accumulator, oil change, sending unit and oil sensor, transmission filter and gasket, a few bloody knuckles, and dirty finger nails. :)

I still say the exhaust is a bit strong but I can live with it for now.

--Steven

[David T]

If you were running over-rich for a while it will take a while for the excess to burn out of the catalytic converter and the smell to go away. You should have some kind of heat shield. You need to use a torque wrench capable of very low torque settings, the torque is 7 ft/lbs, see G:02:02. Pan bolts 2-3 ft/lbs. You must check that the pan is flat and has not been bent from someone overtightening the bolts to try to stop a leak.