Rough idle, NO acceleration

[Carbuilder]

Hi Guys,

I've had my car for a few months now and I've put 1,000 Kms on it, it runs and drives perfectly, and I really like it. BUT...

Today I went to start it and it started fine, but the idle was a little rougher than usual. But there was no acceleration. Pressing the gas pedal only made the idle much, much worse (shaking a lot), to the point of almost dying. Probably would have died if I kept at it. Pressing the pedal very slowly or faster didn't seem to make a difference. After a few minutes of my trying to drive back into the garage, I think it sorted itself out. I revved it a few time before shutting it off and it was OK. I started it a few hours later and the same rough idle, no acceleration was back.

I'm new to these cars but couldn't see anything obvious that had disconnected and nothing was done in the way of work on it since it was running well.

Ideas on what I should check?

Rick
Ontario, Canada
ps. it's a Canadian car if that matters.

[David T]

With the motor running, see if you can hear the frequency valve on the R/H valve cover buzzing.

[Helirich]

The warm up regulator could be acting up. If the electric heater part doesn?t work, it will warm up from the valve cover and run fine. The colder the car, the longer it takes.

[Carbuilder]

Ran it again this morning...same thing. Starts right up, lumpy idle, and won't accelerate. When pressing the gas pedal slowly the RPM will increase very slightly from around 700 to 800, running much rougher, and any more pressing and it will die.

After it warmed up for maybe 5 minutes it ran OK. Not sure if it was perfect (didn't take it for a drive, just revved it in the garage), but it would rev up and idle; idle maybe a little lower than normal.

Not sure what I am supposed to be listening for. Is this the FV, whatever is wrapped up in here:

70873

70874

If so, I couldn't hear anything or feel any vibration from it, before or after the engine was warmed up. My exhaust is not stock and is a bit loud, but even using a hose up to my ear I couldn't hear anything.

Rick

[mhanch]

mine did this when i had a vacuum fitting come loose. check behind the engine. those get brittle and fall off their connectors sometimes.

[Carbuilder]

Don't think a vacuum leak would fix itself every time after warming up.

Should there be voltage across these 2 connectors with the ignition on, or only with the engine running? I have no voltage with the ignition on, engine off.

70875

I checked all of the fuses. Should I check any particular relay? If so, how?

70876

I appreciate the help.

Rick

[FABombjoy]

Don't think a vacuum leak would fix itself every time after warming up.
It will if it's a vacuum line connected to the cold accel enrichment part of the warm-up regulator.

No enrichment will behave as described. The engine instantly leans out on throttle tip-in and stumbles.

[Bitsyncmaster]

Should there be voltage across these 2 connectors with the ignition on, or only with the engine running? I have no voltage with the ignition on, engine off.

Rick

The frequency valve only gets power with the engine running. Or cranking the starter.

[Carbuilder]

More info,

With the engine running I pulled off each of these connectors in turn and it didn't do anything. Should it with the engine cold?

Circled connectors:

70877

The arrow points to something that doesn't look stock. A line (vacuum?) comes out of the right side of the valve, then has a filter or something, then "T's" into a line coming from the other side of the valve...with black tape holding it together. Keep in mind I haven't changed anything and the car was running fine.

Both of those lines then go off with the red one towards the front of the engine, and then down somewhere. Is there a lot wrong with this?

70878

I'll check for voltage on the FV with the engine running tomorrow.

[Carbuilder]

Found this info on the warm up regulator. Sounds exactly like my issue.

?If the vacuum hoses are not properly connected, or if there is a fault in the vacuum circuit (failed thermal vacuum switch, cracked hose, loose hose, missing or backwards delay valve) the car will be almost undriveable (will stall on any acceleration) until the regulator warms up, and may then be just fine.?

[Helirich]

Found this info on the warm up regulator. Sounds exactly like my issue.

?If the vacuum hoses are not properly connected, or if there is a fault in the vacuum circuit (failed thermal vacuum switch, cracked hose, loose hose, missing or backwards delay valve) the car will be almost undriveable (will stall on any acceleration) until the regulator warms up, and may then be just fine.?

Sounds kind of like what I said in the third post.

[Carbuilder]

Sounds kind of like what I said in the third post.

I know. I'm slowly learning about the different systems in the car. When someone suggests something I have to first find out what they are talking about, read up on it, find where it is on the car, then see how to find out if it isn't working properly. So not ignoring suggestions, just in the learning while troubleshooting phase.

Edit: How do I know if it is the warm up regulator? I took the tape off and it looks OK. Don't see any cracked or disconnected lines. Where does the other hose go to, after the 'T'? Just to atmosphere?

70879

Rick

[Carbuilder]

No voltage to the FV when running.

70880

[Bitsyncmaster]

No voltage to the FV when running.

70880

The RPM relay turns on the lambda (main fuel) relay when the engine is running. Then the lambda relay powers both the lambda ECU and FV. You should be seeing around 6 volts on the FV. It's not 12 because it will be switching on and off at 100 Hz.

So check both the RPM relay and lambda relay. Also make sure your lambda grounds are connected to the engine block (passenger side on intake manifold).

[dn010]

Also check the condition of those lousy bulkhead connectors, mine gave me all sorts of electrical trouble.

[Carbuilder]

I checked the Lambda relay and it is good; took it out and tested it.

Made a jumper for the RPM relay to test that:

70883

No difference, car runs the same.

I was reading about the various fuses and saw that #7 controls the fuel pump and a lot of other related circuits. Checked my fuse panel and saw a melted area instead of a fuse. That explains the external 20A fuse wired into the brown wires:

70884

I took the tape off the connections, tested the fuse and holder, and gave the crimps an extra squeeze. Car still runs like crap. What else controls those circuits?

Rick

[Carbuilder]

Also check the condition of those lousy bulkhead connectors, mine gave me all sorts of electrical trouble.

I'll do that. I'll give them a spritz of Deoxit (amazing stuff).

[Bitsyncmaster]

I checked the Lambda relay and it is good; took it out and tested it.

Made a jumper for the RPM relay to test that:

70883

No difference, car runs the same.

I was reading about the various fuses and saw that #7 controls the fuel pump and a lot of other related circuits. Checked my fuse panel and saw a melted area instead of a fuse. That explains the external 20A fuse wired into the brown wires:

70884

I took the tape off the connections, tested the fuse and holder, and gave the crimps an extra squeeze. Car still runs like crap. What else controls those circuits?



Rick
So your still not getting voltage on the FV? One pin will have 12 volts to ground, the other would be switching from ground to floating at 100 Hz. Are you sure your lambda relay is the proper type. It is different than all the other relays.

[Carbuilder]

Also check the condition of those lousy bulkhead connectors, mine gave me all sorts of electrical trouble.

The other day, being fairly new to the Delorean, I was poking around the engine compartment and took the air cleaner cover off to see what the filter looked like and also the throttle body.

The day after when I went to start it, it was behaving as described. I thought maybe I disturbed something in removing the air cleaner housing, so took it off again to have a good look around. Nothing apparent.

After all the tests and checks I've done to try and sort out the issue, it seemed that everything was working as far as the fuse/relay area goes, but the engine wasn't getting the electrical power it needed for the various systems. So I thought it must be something between the 2 areas. But I didn't give it enough thought until I saw the post about checking the bulkhead connectors.

Then I remembered, when I took the air cleaner assembly off, I was curious what was behind the metal shield in the corner of the compartment. I took that off and had a look inside. I did have some trouble removing it and then getting it back in place, but didn't think much about it.....until now.

Then the pieces came together. An issue between the fuse area and the engine area. I might have disturbed a marginal bulkhead connection without knowing it. Every other check came out OK.

Went back into the garage, took the cover off, removed each connector in turn and gave each one a shot of Deoxit. Started the car and it is back to normal!! I can hardly believe it. I didn't take it for a drive yet, but it would rev cleanly which it wouldn't do before.

So thank you very much for all the help and suggestions. Even the ones that turned out to not be an issue gave me a chance to learn more about the various systems and how to check them in the future.

And if anyone is not familiar with this stuff:

70885

Buy some. It isn't cheap but it has worked miracles for me. It has solved a number of connection issues I've had over the years. Works on so many things...check the reviews. Whenever I pull a connection apart or remove a relay, it gets a shot of that.

Until the next issue,

Rick
ps. I do have a very strange one that I'll post about later.

[David T]

It usually turns out to be something that was disturbed recently. If you have bad/dirty/loose connections the ultimate solution is not a spray but tightening and cleaning the connection or it may come back again in the near future. The Lambda system uses low voltages so it is especially susceptible to bad connections. This is just one of the things you have to do to sort out an old car. Now that you can hear the frequency valve you will immediately know if it is the problem in the future. It makes a distinctive sound. Congratulations on your persistence. It is very gratifying to actually find and fix a problem.

[dn010]

Glad it worked out for you and it was something that didn't cost hundreds to fix. The bulkhead connectors are garbage. I know, lots of people don't have an issue with them on their cars but I did, and constantly. Those connectors should have been weatherpacks from the start.

[Helirich]

And if anyone is not familiar with this stuff:

70885

Buy some. It isn't cheap but it has worked miracles for me. It has solved a number of connection issues I've had over the years. Works on so many things...check the reviews. Whenever I pull a connection apart or remove a relay, it gets a shot of that.

Where do you buy it?

[dn010]

Amazon.

[Timeless]

Glad it worked out for you and it was something that didn't cost hundreds to fix. The bulkhead connectors are garbage. I know, lots of people don't have an issue with them on their cars but I did, and constantly. Those connectors should have been weatherpacks from the start.
Deutsch connectors are the best.

[DMCVegas]

And if anyone is not familiar with this stuff:

70885

Buy some. It isn't cheap but it has worked miracles for me. It has solved a number of connection issues I've had over the years. Works on so many things...check the reviews. Whenever I pull a connection apart or remove a relay, it gets a shot of that.


At work I end up consuming cans of this stuff on a regular basis on old equipment. It?s insane the amount of oxidation that collects in electronics. Especially sliders and rotary pots on audio gear in smoky environments.

Two worst spots on the DeLorean for electrical connections are the bulkhead connectors in the engine bay, and the radiator bracket up front where everything gets grounded. Both areas are the worst as being subjected to corrosion from road spray.

[David T]

At work I end up consuming cans of this stuff on a regular basis on old equipment. It?s insane the amount of oxidation that collects in electronics. Especially sliders and rotary pots on audio gear in smoky environments.

Two worst spots on the DeLorean for electrical connections are the bulkhead connectors in the engine bay, and the radiator bracket up front where everything gets grounded. Both areas are the worst as being subjected to corrosion from road spray.

The fuse block/relay area is also a common source of trouble too. The blades of the fuses can build up a layer of oxide and cause bad connections and heat. Especially circuit # 7 when the fuel pump goes bad and starts drawing a LOT of current and the cooling fan circuit with the aptly named and notorious blue Fan Fail Relay. People think a 40 year old electrical system doesn't need any care or maintenance. Just put a new battery in the car and everything should be "Good To Go"! Because the car has a plastic tub underbody, grounding is especially important in a Delorean. Because several circuits go to common grounding points, when the ground is not good the circuits backfeed into other circuits and can cause all kinds of weird symptoms. There is also that plug in the front facia that feeds the fuel pump that can corrode and then the pump won't run. When you find a Delorean that has sat for a long time rodents get into the hidden areas and cause all kinds of mayhem from chewing up the wires to urinating and corroding everything!