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

  1. #21
    Stupid Newbie DaraSue's Avatar
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    Quote Originally Posted by Bitsyncmaster View Post
    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?

  2. #22
    Senior Member Bitsyncmaster's Avatar
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    Quote Originally Posted by DaraSue View Post
    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.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  3. #23
    Stupid Newbie DaraSue's Avatar
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    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.

  4. #24
    Stupid Newbie DaraSue's Avatar
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    Just now I tried holding the plate open as suggested in this post: http://dmctalk.org/showthread.php?14...l=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.
    Last edited by DaraSue; 03-20-2017 at 01:28 PM.

  5. #25
    Stupid Newbie DaraSue's Avatar
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    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?

  6. #26
    Delorean Guru
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    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.
    David Teitelbaum

  7. #27
    Stupid Newbie DaraSue's Avatar
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    Quote Originally Posted by David T View Post
    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.

  8. #28
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    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.
    David Teitelbaum

  9. #29
    Stupid Newbie DaraSue's Avatar
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    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.

  10. #30
    Stupid Newbie DaraSue's Avatar
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    Quote Originally Posted by David T View Post
    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...

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