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Thread: Erratic Idle on 2018 Mustang GT

  1. #1
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    Erratic Idle on 2018 Mustang GT

    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
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  2. #2
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    I have ran into this but only seen it when I was running e85 in my flex file, if I was at e30 or less on the same file it never did it. Never logged it though bc I couldn't duplicate it, would be times it would never do it, then when I dint have my computer with me it would do it. If you put the shifter in Park it stops too, it will idle like normal

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    I thought it was ethanol related as well, however it does it no matter which fuel. I have begun to makes changes in the calibration, changing the mapped point configuration and all associated tables. Watching where it goes during it's fit, and searching as to why. I am trying to remove the ability for it to do so. After reviewing it earlier, it appears the MPs at idle are between 0-2, however during the hiccup, it bounces all over the place. VCT goes from (20,0) at idle to (-20,0) at idle, creating tons of everlap, causing the car to "buck." If I find a remedy, I will post what I've done.

    Kris

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    I have only had it happens when running ethanol, same tune running 93 causes no issues. I haven't spent much time diagnosing it though. Something you could do as temporary work around is set the maps it hops around to the same angles and map 0-2, this way it will hop around maps with the same values as it, same shit we do with ghost cam tunes pretty much.

  5. #5
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    Quote Originally Posted by Jn2 View Post
    I have only had it happens when running ethanol, same tune running 93 causes no issues. I haven't spent much time diagnosing it though. Something you could do as temporary work around is set the maps it hops around to the same angles and map 0-2, this way it will hop around maps with the same values as it, same shit we do with ghost cam tunes pretty much.
    What is very strange is that this issue seems to be getting worse with time. Makes no sense. I made a few adjustments to the areas where it jumps around, and no luck. It still happens, and actually had gotten worse. I flashed the stock tune back to the car for the time being to monitor it closely. Will work up from there.

    Kris

  6. #6
    Have this problem with my personal car. It progressively has gotten worse even with everything back to stock on it. Car even dies periodically while sitting in gear stopped. I see on mine intake cam timing over and under shoots the commanded(20) then starts going to far positive(40) then drops to (-40) and dies. Initially started when car had 3k miles on it now at 14k and is bad to point where it will do it every time almost when stopped and car up to temp. When cold car is perfectly fine. I also see that anything above 1k rpm the cam timing is dead nuts accurate. Looks like a trip to dealer to see what they say maybe new cam phasers will fix it?

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    Quote Originally Posted by MaximumVelocity View Post
    Have this problem with my personal car. It progressively has gotten worse even with everything back to stock on it. Car even dies periodically while sitting in gear stopped. I see on mine intake cam timing over and under shoots the commanded(20) then starts going to far positive(40) then drops to (-40) and dies. Initially started when car had 3k miles on it now at 14k and is bad to point where it will do it every time almost when stopped and car up to temp. When cold car is perfectly fine. I also see that anything above 1k rpm the cam timing is dead nuts accurate. Looks like a trip to dealer to see what they say maybe new cam phasers will fix it?
    yeah, when mine would act up it would only be at operating temp, never when cold.

  8. #8
    I guess I will find out once I get it to dealership in the next week or two. I will update this thread with anything I can find.

  9. #9
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    Quote Originally Posted by MaximumVelocity View Post
    Have this problem with my personal car. It progressively has gotten worse even with everything back to stock on it. Car even dies periodically while sitting in gear stopped. I see on mine intake cam timing over and under shoots the commanded(20) then starts going to far positive(40) then drops to (-40) and dies. Initially started when car had 3k miles on it now at 14k and is bad to point where it will do it every time almost when stopped and car up to temp. When cold car is perfectly fine. I also see that anything above 1k rpm the cam timing is dead nuts accurate. Looks like a trip to dealer to see what they say maybe new cam phasers will fix it?
    That is exactly what mine is doing. I took a video of mine earlier, drove it into the garage and it died on me.

    Kris

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  11. #11
    That is exactly what mine does but also dies out occasionally. I did hear there was a similar issue in the ford explorer that a dealer update fixed the issue but so far I haven't seen any TSB's for the problem.

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    Wonderful. I'm currently messing with my calibration, trying different things. It will sit and idle, swinging between MP 0, 1, and 2. Just watch the VCT going from (30,0) to (0,0), all while sitting in my driveway. Makes no sense.

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    Quote Originally Posted by kris5597 View Post
    Wonderful. I'm currently messing with my calibration, trying different things. It will sit and idle, swinging between MP 0, 1, and 2. Just watch the VCT going from (30,0) to (0,0), all while sitting in my driveway. Makes no sense.
    you try setting MAP 0, 1, & 2 to 0,0 and see if it stops not like those maps are much outside of idle anyway, zero the out

  14. #14
    Kris log VCT schedule mode so we can see what vct distance table its trying to use.

  15. #15
    Had the same problem with A customers car but my personal car does not do it. His car even did it with the stock tune. It was mostly his bank 1 VCT that would go crazy and cause the car to die randomly.

  16. #16
    On mine its both intake cams going crazy but they follow each other till they make very large swings then one is smoothly following the other which makes a sharp movement.
    Last edited by MaximumVelocity; 12-29-2018 at 10:17 AM.

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    I'll log the VCT Schedule mode next. I have reconfigured the Optimal Stability VCT load based table and have adjusted MP 0 intake VCT, it appears I am moving in the right direction. Car has not died yet, only one case where it did some funky stuff with the VCT swing before I adjusted MP 0, hasn't hiccuped since I have adjusted it, but I can still watch the VCT swing, just less. I have bumped idle up to 700 rpm from the stock 600 rpm in drive, because it would dip to around 500 when the VCT moves and as it adds timing to control idle. I will log shortly to see if it is better.

    Kris

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    Update... my reconfigured MP and load tables seem to have a positive result. Idle dips a little when coming to a stop, but it seems to be well under control. About to install my PMAS back on the car and continue testing. Car currently has headers and exhaust with the stock intake.

    Kris

  19. #19
    Quote Originally Posted by kris5597 View Post
    Update... my reconfigured MP and load tables seem to have a positive result. Idle dips a little when coming to a stop, but it seems to be well under control. About to install my PMAS back on the car and continue testing. Car currently has headers and exhaust with the stock intake.

    Kris
    Do you mind showing what you changed by posting tune? Mine is getting worse and does it even when cold now. It also has thrown random misfire code and shows pending codes for p0011, p0012, p0021, p0022, which are camshaft timing over advanced and camshaft over retarded codes for both banks. Car gets pretty rough and also lurches a bit when on the brake form this.

  20. #20
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    I PM'd you.