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

  1. #11
    Stupid Newbie DaraSue's Avatar
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    Quote Originally Posted by David T View Post
    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.

  2. #12
    Junior Member
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    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.
    --
    Mike

  3. #13
    Delorean Guru
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    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!).
    David Teitelbaum

  4. #14
    Senior Member Bitsyncmaster's Avatar
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    Quote Originally Posted by David T View Post
    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).
    Dave M vin 03572
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  5. #15
    Sometimes Owner louielouie2000's Avatar
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    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.
    Last edited by louielouie2000; 03-17-2017 at 04:00 PM.
    Louie Golden

  6. #16
    Senior Member Bitsyncmaster's Avatar
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    Quote Originally Posted by louielouie2000 View Post
    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.
    Dave M vin 03572
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  7. #17
    Senior Member MML's Avatar
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    Quote Originally Posted by DaraSue View Post
    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.
    - Martin - VIN 5436 -

  8. #18
    Stupid Newbie DaraSue's Avatar
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    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:


    I guess it's not as obvious here but I definitely noticed it IRL.
    Last edited by DaraSue; 03-18-2017 at 01:58 PM.

  9. #19
    Senior Member Bitsyncmaster's Avatar
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    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.
    Dave M vin 03572
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  10. #20
    Stupid Newbie DaraSue's Avatar
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    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...gnition-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?

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