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Thread: 2018 Mustang GT Idle Hang/Runaway

  1. #1
    Tuner evolmotorsprt's Avatar
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    2018 Mustang GT Idle Hang/Runaway

    I was working on a 2018 mustang Gt today that has had a checkered life... Flood salvage, Bad tune etc...
    Car has CAI and catted longtubes

    The last tuner tuned the MAF with a leak in the couplers on the cold air intake. The CAI couplers were fixed and I reverted most of the tune to stock and fixed the transport delay.
    Now that the car wasn't going immediately into limp mode I noticed the idle RPM creeping up as high as I'd let it go. I could get it to come back down by blipping the throttle. It would idle correctly for ~15sec and start climbing again. I noticed that the Idle speed control mode would switch from "RPM Control" to "RPM Control No Learning." I sprayed brake clean all over to try to find a vacuum leak but couldn't

    The car is also commanding an incredibly rich lambda even though the widebands are reading 1.0.

    Here's the as found, my fixes, and a log of the issue. Thanks for any ideas.
    Attached Files Attached Files

  2. #2
    Advanced Tuner
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    New Orleans, LA
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    if the spark tables are kicked up too much on decel it can cause idle hang too
    decipha @ EFIDynoTuning
    http://www.efidynotuning.com/

  3. #3
    Tuner evolmotorsprt's Avatar
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    Quote Originally Posted by decipha View Post
    if the spark tables are kicked up too much on decel it can cause idle hang too
    The spark should be stock values everywhere. I can check again when I'm at my laptop. I'm really thinking there has to be a leak somewhere post MAF, or maybe in the card slot itself.