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Thread: Idled high before turning engine off, and now it wonít start

  1. #1
    Senior Member
    Join Date:  May 2011

    Location:  Norton, MA

    Posts:    883

    My VIN:    767 (3.0L EFI/EDIS)

    Idled high before turning engine off, and now it wonít start

    This is my 3.0L conversion. I went to the grocery store and got there without issue, but when I put the car in Park (automatic transmission) the RPMs went up to over 2000. I turned it off and tried to start it again, but it would just crank and never actually catch.

    I did my shopping and tried again, but still nothing. Of course I didnít bring my laptop with me, so I canít get any information out of MegaSquirt. I made sure I have fuel in the tank, and my fuel pressure gauge shows that I have good pressure, so itís not that.

    Given the high idle before I shut it off, Iím wondering if thereís a vacuum leak or a stuck IAC, but Iím grasping at straws here. I didnít see anything obvious when I looked in the engine bay.

    AAA is on the way to tow me home, but I thought Iíd see if anyone had any other ideas about what I could check.

    Thanks!

    ó Joe

  2. #2
    Senior Member Citizen's Avatar
    Join Date:  Jun 2011

    Location:  Houston, TX

    Posts:    737

    High idle before shutdown sounds like too much fuel to me (maybe stuck throttle), and might also account for almost, but not quite being able to restart (flooded). Probably should have waited like 30 minutes then attempt restart again. Or blow ample fresh air into the intake and try again.

    Good luck.

    Thomas

    ...
    Keeper of the DeLorean Owners Directory, at www.DeloreanOwnersDirectory.net

  3. #3
    Senior Member
    Join Date:  May 2011

    Location:  Norton, MA

    Posts:    883

    My VIN:    767 (3.0L EFI/EDIS)

    When I got to the store, I turned off the engine then immediately tried to start it again. I cranked about 10 times before I decided to just go shopping.

    I think I was in the store for 15 minutes or so, which may not have been enough time to let any extra fuel evaporate. I was able to take off the air intake and could see that the throttle was properly closed. However, I don't know if the IAC is actually closed, or if there's a vacuum leak elsewhere. I also tried pressing the pedal to change the volume of air going on, but that didn't do anything -- I mean, my problem appears to be too much air, at least for the high idle bit.

    I wasn't able to test spark in the parking lot, which I more want to do for completeness than thinking anything is wrong with it. I have to find my engine bay ignition push button and keep in my on-the-road repair kit for the next time something like this happens.

    AAA towed me home, so at least I'm not stuck at the store anymore. I'm going to have to wait until the weekend to do any more diagnostics (it's raining until then, and my new garage is still being built). Then I'll be able to plug in a laptop and hopefully get some more information about what it thinks it's doing, while I also look at the hoses and IAC for where the extra air might be coming from.

    Thanks!

    -- Joe

  4. #4
    Senior Member
    Join Date:  May 2011

    Location:  Norton, MA

    Posts:    883

    My VIN:    767 (3.0L EFI/EDIS)

    I realized I should be more clear about the symptoms: The starter cranks, but at no point does the engine actually fire -- it just cranks and cranks and cranks. There's never a point where even one cylinder fires and it goes back to cranking. It's purely the starter turning the engine, and that's it.

    -- Joe

  5. #5
    LS Swapper Josh's Avatar
    Join Date:  Mar 2013

    Location:  SK, Canada

    Posts:    2,079

    My VIN:    11408

    Club(s):   (TXDMC) (DOI)

    Check the MS is seeing RPM. If it is not getting a signal from the crank sensor it will not spark.
    In regards to the high idle ensure the operation of the IAC, you can also do this in tunerstudio. Also check for vaccum leaks in general.
    Seems like two different problems.

    I sometimes had a no start condition with the 3.0 and it was always to do with the bulkhead connection for the crank sensor.

    5.3L LS4 + Subaru 6spd 314whp/348ft-lbs
    Getting it back on the road!
    LS Swap

  6. #6
    Senior Member
    Join Date:  May 2011

    Location:  Norton, MA

    Posts:    883

    My VIN:    767 (3.0L EFI/EDIS)

    Well this is embarrassing. I spent twenty minutes today trying to get two different laptops to connect. I finally tugged on the MS box and the DB38 just fell out. Plugged it back in and it fired right up with the correct idle and everything. I just have forgotten to screw the connector back in last time I took it out of the car.

    Thanks for the help nonetheless. This time it was just stupid user error.

    ó Joe

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