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Thread: Bad Gas? Or something else...

  1. #1
    Senior Member DL4567's Avatar
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    Bad Gas? Or something else...

    Hi guys,

    TL;DR version: Engine hesitates when revved above idle. Sounds like it will stall. Bad gas? Or look for other things? (video link below)


    Long version:
    I went to drive my car today to give it some exercise, and for the first time in 16 years of ownership, it had a problem that kept me from leaving the driveway. After 10 minutes or so of letting it idle and messing with it, I ended up putting it back in the garage. I'm *hoping* it's as simple as bad/old gas, but wanted to ask on here and get some opinions.

    Admittedly I'm getting worse these past few years of not driving it enough, and only get it out about every 1-2 months. But it has always been reliable, and if it's a longer interval, it might stall after the first starting try (automatic transmission), but it always runs great after the 2nd try on those occasions. Today it had been 7 weeks since I drove it last, and anticipating a stall on the first turnover I gave it a bit of gas to keep it running. There was a bit of a "pop/ping" noise from the engine as it turned over, which was unusual. It wasn't super loud or anything, but it bothered me because I haven't heard it before on startup. After that, it just settled in to 750 rpms and stayed there. It did NOT do the normal rpm-hunting that it typically does on every cold start in my ownership. But ok, I shrugged it off, and backed out of the garage. All seemed fine just letting off the brake and letting the idle speed move the car.

    When I wanted to actually drive out of the driveway and put some load on the engine, is when I realized that when you press on the gas pedal, it stumbles and gets very hesitant, and sounds like it will stall. No matter how many times I tried, even after warming up for 10 min, raising it just above idle stumbled pretty bad. In neutral, it seems to be smoother if you get it up to 2,000 rpm or so, but no dice between 750 and 2,000.

    The gas tank was last filled 4 months ago in August, and has been on 1/2-5/8 of a tank for maybe 2 months or so. I googled and see that gas can go bad in 3-6 months, but this interval is nothing I haven't done many times before for years and years with no problems. Also, not sure if it's of any significance, but this was the first "cold weather" startup this season on it. 7 weeks ago, it was much warmer weather.

    Here's a short video. It really doesn't sound that bad on camera, but under load when trying to drive, the engine sounds like it will stall.

    https://youtu.be/1WxIcD_eVcs

    Am I on the right track to siphon out the gas, put in fresh and see what happens? Thanks all, for your help.
    Last edited by DL4567; 12-21-2020 at 01:19 AM.
    Derek L
    VIN 5302

  2. #2
    Senior Member
    Join Date:  Jul 2012

    Location:  Thousand Oaks, CA

    Posts:    206

    My VIN:    16563

    Hi, I know with my car if i start it cold like that and let it idle, it takes a long time to get up to regular operating condition. Right now I have the center console so I can see the light from the bulbs. When I start the car those bulbs turn on but only when I rev the car to over 3k ish, the bulbs all get brighter and stay that way and the car runs normal. I noticed on your youtube video you only applied a little acceleration, but if you apply a higher rev like I do, does it settle back to a more normal idle?


    Quote Originally Posted by DL4567 View Post
    Hi guys,

    TL;DR version: Engine hesitates when revved above idle. Sounds like it will stall. Bad gas? Or look for other things? (video link below)


    Long version:
    I went to drive my car today to give it some exercise, and for the first time in 16 years of ownership, it had a problem that kept me from leaving the driveway. After 10 minutes or so of letting it idle and messing with it, I ended up putting it back in the garage. I'm *hoping* it's as simple as bad/old gas, but wanted to ask on here and get some opinions.

    Admittedly I'm getting worse these past few years of not driving it enough, and only get it out about every 1-2 months. But it has always been reliable, and if it's a longer interval, it might stall after the first starting try (automatic transmission), but it always runs great after the 2nd try on those occasions. Today it had been 7 weeks since I drove it last, and anticipating a stall on the first turnover I gave it a bit of gas to keep it running. There was a bit of a "pop/ping" noise from the engine as it turned over, which was unusual. It wasn't super loud or anything, but it bothered me because I haven't heard it before on startup. After that, it just settled in to 750 rpms and stayed there. It did NOT do the normal rpm-hunting that it typically does on every cold start in my ownership. But ok, I shrugged it off, and backed out of the garage. All seemed fine just letting off the brake and letting the idle speed move the car.

    When I wanted to actually drive out of the driveway and put some load on the engine, is when I realized that when you press on the gas pedal, it stumbles and gets very hesitant, and sounds like it will stall. No matter how many times I tried, even after warming up for 10 min, raising it just above idle stumbled pretty bad. In neutral, it seems to be smoother if you get it up to 2,000 rpm or so, but no dice between 750 and 2,000.

    The gas tank was last filled 4 months ago in August, and has been on 1/2-5/8 of a tank for maybe 2 months or so. I googled and see that gas can go bad in 3-6 months, but this interval is nothing I haven't done many times before for years and years with no problems. Also, not sure if it's of any significance, but this was the first "cold weather" startup this season on it. 7 weeks ago, it was much warmer weather.

    Here's a short video. It really doesn't sound that bad on camera, but under load when trying to drive, the engine sounds like it will stall.

    https://youtu.be/1WxIcD_eVcs

    Am I on the right track to siphon out the gas, put in fresh and see what happens? Thanks all, for your help.
    1983 Delorean-auto, black/gray int. 38k miles

  3. #3
    Under Ron's watchful eye. Glory be to Ron! Michael's Avatar
    Join Date:  May 2011

    Posts:    4,251

    My VIN:    A bunch of numbers and letters that should not interest you.

    What you are experiencing could be contaminated gas but it could be many other things as well. I would not immediately suspect contaminated/water in the gas as it is rare. I would look for vacuum leaks first. Checking(not setting or adjusting) the dwell might zero you in on the problem.

    If it runs and idles decently but gets worse under a load or acceleration I would suspect in order:

    Low battery voltage (check battery and alternator output)
    Vacuum leak (especially in the back on the distributor advance or the cpr)
    Fuel filter dirty
    Ignition problem (possibly bad coil or broke /cracked dist. cap or burnt rotor)

  4. #4
    EFI'd dn010's Avatar
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    Location:  Florida: Pinellas County

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    You can typically smell that old stale gas smell in the exhaust if the gas is bad. If it sat for two months with gas containing ethanol then it is bad, I find it starts turning in a matter of weeks.
    -----Dan B.

  5. #5
    Senior Member
    Join Date:  Jan 2019

    Posts:    127

    As others have said could be a number of things including bad gas but you need to run through all the test. Test your fuel pressures and also flow patterns and rates from the Injectors because uneven flow rates and patterns can cause this.

  6. #6
    Delorean Guru
    Join Date:  May 2011

    Location:  Northern NJ

    Posts:    7,922

    My VIN:    10757 1st place Concourse 1998

    The two most likely causes are;
    Stale gas
    Stuck plunger in fuel mixture unit

    Other possibilities include;
    Low battery
    Vacuum leak
    CPR out of calibration
    Fuel injectors dirty
    David Teitelbaum

  7. #7
    Senior Member
    Join Date:  Jul 2012

    Location:  Thousand Oaks, CA

    Posts:    206

    My VIN:    16563

    Could the fuel accumulator be in that list of possible issues?

    Sent from my SM-N976U using Tapatalk
    1983 Delorean-auto, black/gray int. 38k miles

  8. #8
    DMC Midwest - 815.459.6439 DMCMW Dave's Avatar
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    Quote Originally Posted by artisticent View Post
    Could the fuel accumulator be in that list of possible issues?

    Sent from my SM-N976U using Tapatalk
    Not likely.
    Dave S
    DMC Midwest - retired but helping
    dswingle@DeLorean.com

  9. #9
    Senior Member DL4567's Avatar
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    Thanks for the responses everyone, it is much appreciated! It's gonna be a busy next few days with Christmas, but I will try and swap out the gas for fresh, check that the plunger isn't stuck, and report back. If that doesn't help, I'll start exploring the other possibilities mentioned. FWIW, the battery should be good as it's a fairly new Optima yellow top, and I keep it disconnected with a kill switch when the car's not in use.
    Derek L
    VIN 5302

  10. #10
    Delorean Guru
    Join Date:  May 2011

    Location:  Northern NJ

    Posts:    7,922

    My VIN:    10757 1st place Concourse 1998

    Just because you have a "fairly" new battery and you disconnect it doesn't mean it can't be low on charge. A battery loses it's charge over time even if you don't use it. You should get it fully charged. Get a Battery Tender or something like it and keep the battery fully charged when the car is not in use.
    David Teitelbaum

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