Car starts but dies when I take my foot off the gas

[DaraSue]

Starting a new thread because the old one (http://dmctalk.org/showthread.php?14884-How-long-before-attempting-restart-after-flooding-engine/page4) had drifted off the original topic.

The story so far: Car wouldn't start the day after getting home from a 400 mile road trip segment (out of 700 total). Found a melted plug at the resistor end of the Y/W wire between the ignition resistor and the coil. Re-terminated the wire, car still wouldn't start. It would catch if I kept my foot on the gas but die as soon as I let off. I'd had a starting problem while on vacation but it started and ran a couple hours later, with no significant issues on the trip home (San Diego to SLC).

This morning, I was able to keep it running with my foot on the gas, enough to back it out and then pull back into the garage (it died once and I coasted back in part of the way). Just now I tried it again, with the air filter off to check the mixture flap, as advised by Mike at MW. This time, it actually stayed running at idle, although low and rough. I didn't leave it running long. It took a little bit of pressure to open the flap on the mixture control afterward.

Has anybody seen this issue before? The filter was a little dusty but not horrifically bad. The fat plastic hose from the side air intake wasn't clamped on, though. I didn't see anything obviously clogging the filter.

Pix of the wiring by the mixture flap and the filter:

49574495754957649577

[DaraSue]

Also for those of you just joining this saga, I had tried the plug swap before and it still wouldn't start.

[louielouie2000]

Did you switch back to a Bosch coil yet? I know my first DeLorean stopped running when I swapped in an aftermarket high performance coil. As soon as I replaced the 20 year old coil, the car cranked right up.

[DaraSue]

Did you switch back to a Bosch coil yet? I know my first DeLorean stopped running when I swapped in an aftermarket high performance coil. As soon as I replaced the 20 year old coil, the car cranked right up.

I never did change the coil. I wasn't sure the new one would work since the specs looked slightly different than what was in the shop manual so I took it back and ordered a Bosch one from DMCCA.

My car has a blue scotch-lock tap holding the ballast resistor wires together, it was on my list of things to have fixed but then I had the overheat issues and it fell by the wayside. It still appears to be intact but should I try opening it up and see if something came apart in there? I was hesitant to try soldering it myself but maybe I can do it. I bought some supposed automotive solder at Wal-Mart just in case.

[opethmike]

Scotch locks are HORRIBLE. Definitely change those; they're a great way to get flaky connections.

[DaraSue]

I bought 3M rosin core solder, is that the right thing? And will an electronics soldering iron do the job?

Also does anybody remember what component the poster was talking about here? http://dmctalk.org/showthread.php?8771-Possible-Bad-RPM-Relay-Car-starts-but-immediately-dies-after-Coil-swap&p=128623&viewfull=1#post128623 The picture 404s but I'm wondering if it could be the same thing in my car since his is a couple numbers from mine. Maybe the wiring guy was hungover that day? (I PMed the poster but he hasn't been on here for a few months.)

[Horsebox]

It reads like he's talking about the electrical connector that plugs into the vacuum advance solenoid, which is behind the fuel distributor. It's tucked away behind and slightly below the distributor but you can get at it by leaning over the engine. It should have one electrical connector and two vacuum hoses plugged in.

Its role in life is to allow the intake vacuum to get at the ignition distributor to give you more ignition advance when the throttle is off idle and the idle microswitch is open.

[DaraSue]

I actually got it started up and drove around a little today. It ran rough and idled low at first but by the time I drove for about 10 minutes it seemed to be idling normally. I took it to my mechanic to get his opinion if the oil had gas in it, and he thought it may have a little and recommended changing it in a few hundred miles. Mike said he thought I should do it in the next one or two hundred miles too, since it didn't look like it was overly full.

I drove about 10 miles from the shop to work and it ran ok. Still getting a whiff of gas in the cabin though. Time to have somebody start looking at the fuel pump?

We'll see what happens when I go home tonight.

A couple of people in the previous thread said that it's not possible to flood a fuel-injected car, but what do you call it when it's got too much unburned gas in the engine? That was Mike's theory about what the problem might have been when I was trying to start it before & after replacing the melted plug. Weird.

I'll probably still try replacing the old coil with another Bosch one just in case.

[Bitsyncmaster]

I bought 3M rosin core solder, is that the right thing? And will an electronics soldering iron do the job?

Also does anybody remember what component the poster was talking about here? http://dmctalk.org/showthread.php?8771-Possible-Bad-RPM-Relay-Car-starts-but-immediately-dies-after-Coil-swap&p=128623&viewfull=1#post128623 The picture 404s but I'm wondering if it could be the same thing in my car since his is a couple numbers from mine. Maybe the wiring guy was hungover that day? (I PMed the poster but he hasn't been on here for a few months.)

Rosin core solder is correct for electrical work. Lead tin solder will solder at a lower temperature than no lead solder. Soldering wires usually takes a lot of heat (large tip and or large wattage iron). The small 19 AWG wires will solder easy but our bare copper wire needs to be cleaned with sandpaper to get good solder joints. For larger wires I use a 200 watt soldering gun. Battery wires I use a very large soldering iron that has a two pound tip and 175 watts of power.

[David T]

Check to see if the frequency valve is buzzing. If it isn't the motor will run too lean and keep stalling. Often you can get it going again by removing and replacing the plug on it a couple of times, the connections get dirty. If that doesn't get it going you will have to trouble-shoot the problem till you can get it to buzz.

[DaraSue]

Check to see if the frequency valve is buzzing. If it isn't the motor will run too lean and keep stalling. Often you can get it going again by removing and replacing the plug on it a couple of times, the connections get dirty. If that doesn't get it going you will have to trouble-shoot the problem till you can get it to buzz.

I hear a humming noise when the car first starts, would that be it, or is it more of an actual buzz?

The car still started rough after my shift last night (sat for 8 hours). Another engineer friend and DeLorean/cars in general buff suggested this could be a symptom of watered-down gas - it sits for a while and the water settles to the bottom of the tank but then gets stirred up when it runs for a little while. I did get my last fillup at a station in the middle of nowhere so it's not outside the realm of possibility. Going to try adding some Heet and see what happens.

[Mike Griese]

Is the buzzing from the front of the car or the engine compartment? If it is the front, that's the fuel pump. If it's the rear, it could be the frequency valve.

[David T]

It is doubtful it is a problem with the fuel. The pump recirculates so anything on the bottom gets well mixed in. The frequency valve does buzz and it is loud enough that you know it when you hear it (when it is working of course!).

[Bitsyncmaster]

It is doubtful it is a problem with the fuel. The pump recirculates so anything on the bottom gets well mixed in. The frequency valve does buzz and it is loud enough that you know it when you hear it (when it is working of course!).

Frequency valve only will buzz with the engine running so you may not hear it unless you use the touch it with a screwdriver and touch the handle end to your ear.

Water and gas don't mix very well. Water will settle to the bottom of the tank very quickly. But today's car gas has ethanol which absorbs water and that pretty much took care of water problems (don't think they sell "dry gas" anymore).

[louielouie2000]

So the frequency valve makes a very distinct chattering buzz- some compare it to an angry cricket or an old timey washboard sound. It's a much more mechanical sound than the fuel pump, which is an electronic whir.

[Bitsyncmaster]

So the frequency valve makes a very distinct chattering buzz- some compare it to an angry cricket or an old timey washboard sound. It's a much more mechanical sound than the fuel pump, which is an electronic whir.

It's a buzz. You can actually power it up by jumping the RPM relay connector without the engine running and hear it better.
Large Brown wire jumped to the double yellow/red wires.

[MML]

This morning, I was able to keep it running with my foot on the gas, enough to back it out and then pull back into the garage (it died once and I coasted back in part of the way). Just now I tried it again, with the air filter off to check the mixture flap, as advised by Mike at MW. This time, it actually stayed running at idle, although low and rough. I didn't leave it running long. It took a little bit of pressure to open the flap on the mixture control afterward.


I had pretty much the same thing happen to me not too long ago. As a test, I removed my RPM relay (the green Volvo one) and popped in the original black factory one (functioning, kept as a spare) and the car was back to normal.
Afterwards I ordered Dave M's solid state RPM relay, fitted it, and the car's been 100% ever since.

[DaraSue]

Put Iso-Heet & filled the tank yesterday, no improvement. Just swapped the RPM relay (both new & old were OEM ones), still tries to quit when I first start up. I think I'm hearing the frequency valve buzz in the back when it's idling. Another issue: I'm seeing the engine vibrate a little. Not massively but enough to be noticeable. I don't remember ever seeing that before, is it a sign that it's firing unevenly or missing?

Video:

https://www.youtube.com/watch?v=gK1SXOB7O3E

I guess it's not as obvious here but I definitely noticed it IRL.

[Bitsyncmaster]

The idle motor hums when the key is on with the OEM idle ECU. Pull your air cleaner to hear the frequency valve mounted on the passenger side valve cover. The FV only buzzes when engine is running. Best to test the buzz with a cold engine since a miss adjusted mixture could make the buzz very soft with a warm engine.

[DaraSue]

Another thing, what's the normal temperature of the exhaust? I looked at the muffler with an infrared thermometer yesterday after driving to work (about 10 miles) and it was reading around 383. This guy talks about unburned gas combusting in the exhaust http://www.tmproductions.com/repairs-and-maintenance-blog/2013/7/28/ignition-issues and I'm wondering if I could be having the same issue.

The lower rear of the engine was around 202. Is this normal?

[DaraSue]

The idle motor hums when the key is on with the OEM idle ECU. Pull your air cleaner to hear the frequency valve mounted on the passenger side valve cover. The FV only buzzes when engine is running. Best to test the buzz with a cold engine since a miss adjusted mixture could make the buzz very soft with a warm engine.

They did make some minor adjustments to the idle control when I was in CA. I'm now back in UT and several thousand more feet above sea level, is it possible that it needs to be adjusted for altitude?

I think I heard the idle motor humming tonight when I turned the key to put the windows up, or at least I heard something humming. It kind of sounded like it was from the front, though.

Speaking of which, another thing which could be a piece of the puzzle or something completely different: Several times now, I've turned the key and nothing's happened. The dash lights come on but the engine doesn't even attempt to start. I normally put the clutch in when I start so I don't think it was a matter of it being in the wrong gear. Now what should I start looking at?

[Bitsyncmaster]

They did make some minor adjustments to the idle control when I was in CA. I'm now back in UT and several thousand more feet above sea level, is it possible that it needs to be adjusted for altitude?

I think I heard the idle motor humming tonight when I turned the key to put the windows up, or at least I heard something humming. It kind of sounded like it was from the front, though.

Speaking of which, another thing which could be a piece of the puzzle or something completely different: Several times now, I've turned the key and nothing's happened. The dash lights come on but the engine doesn't even attempt to start. I normally put the clutch in when I start so I don't think it was a matter of it being in the wrong gear. Now what should I start looking at?

What powers up most things are the two large AUX relays mounted under the relay metal plate. One AUX relay turns on when the key is on it's first "on" position and the second AUX relay when the key is in the further "on" position. Not much goes wrong with those AUX relays it seems. You can try turning you key a very little at a time to get to know what happens.

Some OEM RPM relays prime the fuel pump when that second AUX relay turns on which is a humming sound from the front for about one second.

[DaraSue]

Well, I swapped the coil this morning and that didn't do it, either. The male plug from the blue & white wire going into the negative terminal was looking a little shady so I replaced that too, to no avail. How much green corrosion can be on a plug without causing problems? I saw a spot of it on the plug on the top right side of the ignition resister, but it's that double-plug one and I didn't have any new connectors for it.

[DaraSue]

Just now I tried holding the plate open as suggested in this post: http://dmctalk.org/showthread.php?14884-How-long-before-attempting-restart-after-flooding-engine&p=215336&viewfull=1#post215336 and it wouldn't start at all. I subsequently started by holding the gas down until I could let off without it dying (it was still idling low and rough, and the engine was noticeably vibrating at this point. I think the RPMs were around 600-700 - I know 775 is supposed to be normal but mine has always idled around 1000 +/- a needlewidth or two). I then got out and pushed on the plate a little and it instantly died. Does this mean the mixture or idle settings need adjustment?

Also I listened for the frequency valve with the filter off and it definitely sounded like it was buzzing. I unplugged it a couple times and plugged it back in, it was obviously old but didn't look terribly corroded or dirty. If I need to clean it what do I use?

Also just checked the elevation at my house vs. DMCCA (where the idle was last set) and it's a difference of about 4600 ft. Wondering if that's part of the problem.

[DaraSue]

Mystery solved (hopefully) - apparently it was the warm-up regulator. My local mechanic replaced it, the thermotime switch and the cold start valve and adjusted the idle back down to 775 and it started fine for him this morning. He said my oil was pretty black - AFAIK they changed it while doing everything else at DMCCA so it's been about 1000 miles since then, is that normal?

[David T]

If the motor was running rich it could discolor the oil. If you smell fuel in the oil and the level is high it should be changed again.

[DaraSue]

If the motor was running rich it could discolor the oil. If you smell fuel in the oil and the level is high it should be changed again.

The oil level was just at the top mark cold. I couldn't exactly tell if it smelled like gas but my roommate thought it might a little. My mechanic said he didn't notice an oil smell when I had it in there but I had him change it just in case.

[David T]

I try to get the oil level right in the middle between the full and low marks when cold and level. I check it in the morning BEFORE starting the car, once a week. I do it on all of my cars. I also check the tire pressures once a week along with fluid level checks, glass checks, and light checks. I have seldom gotten stuck on the road, I attribute that to regular checks and maintenance.

[DaraSue]

Well, back to the drawing board... it started hard again today. I didn't let it go long enough to see if it stalled when I let off, but it was idling really low and rough again. The mechanic said it started OK for him yesterday so I feel like I've just forgotten how to start a car or something.

I took it back thinking I'd have him turn the idle back up and see if that helped (he'd set it at 775 but I think Danny set it around 950 and it always idled at 1000+ even before that) but I noticed while he was messing with it that it idled smooth at 775 but fluctuated when it was higher. It seems to run fine when it warms up and I drove it around 60 miles today with no issues so I'm going to call Mike tomorrow and if he doesn't think it's a bad idea to drive that far, plan on taking it back to MW next week and see if they can sort it out.

[DaraSue]

I try to get the oil level right in the middle between the full and low marks when cold and level. I check it in the morning BEFORE starting the car, once a week. I do it on all of my cars. I also check the tire pressures once a week along with fluid level checks, glass checks, and light checks. I have seldom gotten stuck on the road, I attribute that to regular checks and maintenance.

Strangely, the only times I've been stuck by the road in the last 20 years have all been in the last 7 months, and all in the D. This is what happens when you don't drive your car since 1993, apparently...

[DaraSue]

Mystery solved (again) (maybe) - they checked my idle motor and the part where it plugs in was wobbly so it was getting a flaky connection. They replaced it with a new one and it tested good so they're going to try cold-starting it tomorrow morning and see how it does.