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Thread: Erratic Idle on 2018 Mustang GT

  1. #41
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    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
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    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
    Advanced Tuner 4wheelinls1's Avatar
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    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
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    I tried different oil viscosity to test this theory months ago, did not change the outcome unfortunately.

    Kris

  5. #45
    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
    Senior Tuner veeefour's Avatar
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    Ford has been replacing +2018 VCT actuators like crazy on this side of the pond. Might be a good lead.

  7. #47
    Advanced Tuner 4wheelinls1's Avatar
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    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.

  8. #48
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    Fixed bad / stalling stock Idle in my 2020 Mustang GT A10

    Thank you to all that contributed to this thread, as it helped me solve my bad idle.

    I'm in process of full bolt-on NA on my 5.0. With only cat-back exhaust and a ram-air snorkel, the car was stalling in D when warm after coming to a stop fairly regularly. Apologies, no logs before or after, but it was 100% fixed after marking the optimal stability mapped point array to all Mapped point 1 rather than having the variety of points. (see attached) The car was whipping up and down idle, particularly getting low leading to stall many times. This fixed in 100%, the idle is always rock solid now.
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    Formerly tuned LS motors with hpt
    Now tuning "Full Bolt On" 2022 Mustang GT A10 on "E70"

  9. #49
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    My 2019 F150 had the same issue. I got 0012 code for bank 1. I replaced the Intake VCT solenoid and that solved the problem. They really messed up for 2018+ coyotes, where you have to open the valve cover to replace the solenoids.

  10. #50
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    I have to backtrack. While my idle/stall issue is improved from the Optimal Stability mapped point changes, I did encounter a few stalls again. Before the changes, I would have the flaky idle as some have described before it does. Now when it dies, it just seems to get a little low, toward 500rpm and just "lose it" and stall. I'll eventually get some logs. Thank you all.
    Formerly tuned LS motors with hpt
    Now tuning "Full Bolt On" 2022 Mustang GT A10 on "E70"

  11. #51
    Advanced Tuner LastPlace's Avatar
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    What are your intake and exhaust cams doing when this happens?
    Actually not desired

  12. #52
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    Quote Originally Posted by LastPlace View Post
    What are your intake and exhaust cams doing when this happens?
    Actually not desired
    I'll run a log tonight or in the AM. My current configuration has

    VCT Exhaust Cam Phase Angle
    VCT Intake Cam Phase Angle
    VCT Schedule Mode
    Formerly tuned LS motors with hpt
    Now tuning "Full Bolt On" 2022 Mustang GT A10 on "E70"

  13. #53
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    watch your cams when it happens

  14. #54
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    Two logs with stall - Cam angles are rock solid

    I've attached two logs of my prototypical stall event. Car was slightly short of warmed up. Each log start at idle, idling fine, as it always does.
    My issue has always been coming to a stop in Drive. I don't think I've had stalls just initially setting off shifting to D. Thus it is
    always an event after braking or coasting to a stop in Drive.

    The cams are rock solid throughout this, Intake at 20 and Exhaust at 0. This is consistent with my Optimum Stability changes. Before I
    made these changes, I did have some idle fluttering around but that may have not had much or anything to do with why I'm stalling.
    Once RPMs break below about 400, VCT Schedule Mode goes to 'Disabled.' I'm presuming this is just what happens when RPMs are that low.

    MAF looks stable enough, in the ballpark through the event. Roughly 0.5lb/min seen at start idle/Park and in and around when it "loses it"
    which I can only identify by the RPMS starting to go too low and not coming back. I don't see anything odd. O2 look good enough to me.

    Only mechanical modification: Borla S-type cat-back exhaust. Calibration wise, fuel and spark are stock except for a few things like COT. Calibration attached.

    Any looks and ideas would be much appreciated.
    Attached Files Attached Files
    Formerly tuned LS motors with hpt
    Now tuning "Full Bolt On" 2022 Mustang GT A10 on "E70"

  15. #55
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    Can you post your logs in .hpl or .csv?

  16. #56
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    Why are your short term trims out of whack?

  17. #57
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    Here are the hpl files.

    Not sure why the trims are like that. I do have a catch can.. I've double checked it a couple times and feel like connections are all good and not an air leak source. Negative trims seems like it would be opposite of an air leak. I did forget to mention that I do have a "Velossa snorkel" ram-air duct. I can't imagine how it could do hardly spit at low speeds. Stock there already is an air intake extension toward the grille- this duct just extends it a bit to reduce pulling in radiator wash and what not.

    Dean
    Attached Files Attached Files
    Formerly tuned LS motors with hpt
    Now tuning "Full Bolt On" 2022 Mustang GT A10 on "E70"

  18. #58
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    Looks like you figured out why its stalling

    I would put the intake system back to stock and see how it works (pro tip: if it had "radiator wash and what not" stock, there would be a lot of unhappy ford customers)
    Last edited by LastPlace; 01-09-2021 at 11:18 AM.

  19. #59
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    Thanks for your analysis. I'll try eliminating the catch can first. The inlet duct may not be able to be removed without loosening the bumper cover so that's not a quick test.

    The radiator wash is more in terms of the temp of the inlet air, not that the air is turbulent necessarily.

    Thanks again, I'll report back when I can. I do wonder what is about decel that makes this happen... as I don't think it ever would stall when starting (or re-starting) sitting there in D. It has to experience a throttle open/close/decel to spawn the stall.
    Formerly tuned LS motors with hpt
    Now tuning "Full Bolt On" 2022 Mustang GT A10 on "E70"

  20. #60
    Advanced Tuner LastPlace's Avatar
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    It’s pretty common knowledge in the S550 community that the ram air devices cause problems exactly like your problem.

    Another common problem with 2018+ Coyotes is the Cam phasers going bad, You can usually look at the intake him and see you dropping to zero right at the time the idle drops