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Thread: Erratic Idle on 2018 Mustang GT

  1. #41
    Potential Tuner
    Join Date
    Jul 2019
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    1

    We?re you able to find the problem ? I?m having the same problem

    Quote Originally Posted by kris5597 View Post
    Hey guys,

    I have seen some other 2018 S550 owners on the forum complaining about an erratic idle, and unfortunately I am plagued by the same issue. The bad idle seems most frequent with the car in drive with foot on the brake, sitting at a stop. I can watch the VCT go crazy as the erratic idle begins, then the car starts bucking around for a few seconds. Fuel trims and timing go crazy, never seen anything like it. If anyone else has experienced this, please help shed some light on the issue.

    Thank you,

    Kris

  2. #42
    Advanced Tuner
    Join Date
    May 2015
    Posts
    419
    No sir, never found a solution. My theory is that the piston slap I was having caused by out of round/ tolerance cylinder bores, and the material worn off from the cylinder and or piston was circulating throughout the oil system and coating the areas where the cam position sensors were located and causing cam phasing and position detection issues under low rpm and oil flow rates. Interesting theory, but it's the best I could come up. I have sense abandoned the car and issues and got rid of it.

    Kris

  3. #43
    I have the same issue on 2 customer cars, can fix the optimum stability cam position but the car has a tendency to stall but is smooth. I also have a crankshaft variation code in one car that repeats, the car idles well after a relearn until you turn it off and restart it, i assume this relates to crank/cam correlation, could the thin factory oil be causing variable cam control issues?

  4. #44
    Advanced Tuner
    Join Date
    May 2015
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    419
    I tried different oil viscosity to test this theory months ago, did not change the outcome unfortunately.

    Kris

  5. #45
    Tuner in Training
    Join Date
    Oct 2016
    Posts
    42
    Have used better thicker oil and it does help but does not cure it. I have played around with other settings and car does not die anymore but still has the rough idle every once in awhile.

  6. #46
    Advanced Tuner veeefour's Avatar
    Join Date
    Oct 2016
    Location
    Poland
    Posts
    601
    Ford has been replacing +2018 VCT actuators like crazy on this side of the pond. Might be a good lead.

  7. #47
    I was able to stabilize it up nicely with changes to Predicted throttle by reducing the idle torque error to 0 in neutral hot idle, that and Optimal cam posn.