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Thread: Backfire tune while stopped

  1. #1
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    Backfire tune while stopped

    Hello everyone,

    As the title suggest i did a backfire tune to my 15 Grand Cherokee 5.7 and all working well except when the car is fully stopped it doesn't backfire at all it cuts fuel if the ECT is over 176,
    if the ECT is lower than 176 it backfires like i want it but anything over that and nothing happens.

    is there a solution to this problem any help is appreciated.

  2. #2
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    Maybe you've worded it wrong but it sounds like you want backfiring at idle? That'd be a big no no.

  3. #3
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    What i mean is after releasing the throttle the pops or ( backfires ) in an rpm range that i have set,
    If the car is moving and throttle is released within the rpm i have set it backfires like i want it,
    But when the car is at idle after releasing the throttle nothing happens.
    I did a log and the spark is like what i set it's just fuel that cuts off after releasing the throttle if the car is fully stopped,
    If i let the car roll in neutral at speed like 4 km/h or more after releasing the throttle anywhere above 3k rpm it backfires.

    I hope it's clear now

  4. #4
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    same here
    we need help
    the car never backfire from stop only when rolling and changing gear N or deceleration

  5. #5
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    Timing and fueling moves to idle control below a certain mph. Post your tune, some have the option to set idle condition based on rpm instead, which may allow you to get what you want as soon as the rpms rise itll drop idle condition and run the same as rolling.

  6. #6
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    Tried changing the idle to rpm and idle thresh to 800 rpm still nothing

  7. #7
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    post your tune

  8. #8
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    Have you tried completely disabling DFCO (max out ECT...etc)?
    DFCO.JPG

  9. #9
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    Quote Originally Posted by 06300CSRT8 View Post
    post your tune
    I'll try to post it today.

  10. #10
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    Quote Originally Posted by Homer View Post
    Have you tried completely disabling DFCO (max out ECT...etc)?
    DFCO.JPG
    The DFCO is disabled.

  11. #11
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    backfire tune.hpt

    sorry i couldn't uploaded it earlier
    here is my tune.

  12. #12
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    Could it be that you need to set idle VSS to 0 in both these charts?
    idle.JPGFT.JPG

  13. #13
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    Quote Originally Posted by Homer View Post
    Could it be that you need to set idle VSS to 0 in both these charts?
    idle.JPGFT.JPG
    I tried the one under the rpm but didn't try the one under general, gonna try that soon
    Thanks.

  14. #14
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    Thinking about it, changing from 3mph to 0mph probably won't help things as the PCM will eventually see that the vehicle is stopped.

  15. #15
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    Quote Originally Posted by Homer View Post
    Thinking about it, changing from 3mph to 0mph probably won't help things as the PCM will eventually see that the vehicle is stopped.
    Makes sense so what you think should be changed ?
    Does the o2 monitoring has anything to do with it ?

  16. #16
    Senior Tuner SultanHassanMasTuning's Avatar
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    guys, the load at idle is different than when your rolling on a decel.

    log your P ratio or aircharge to see.
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  17. #17
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    Quote Originally Posted by SultanHassanMasTuning View Post
    guys, the load at idle is different than when your rolling on a decel.

    log your P ratio or aircharge to see.
    No argument there, it's just not clear which table(s) needs tweaking at idle? OP already stated that at idle fuel is being cut-off after revving...which is not the case when the car is rolling.

  18. #18
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    Quote Originally Posted by Homer View Post
    No argument there, it's just not clear which table(s) needs tweaking at idle? OP already stated that at idle fuel is being cut-off after revving...which is not the case when the car is rolling.
    That's right the problem is with fuel being cut-off after revving the spark is right where i want it but the fuel that keep it from backfiring.
    In my brother 09 Wrangler there were no problem what so ever when it's stopped i didn't have to change anything,
    But in my 15 Grand Cherokee it seems like it's connected with the coolant temp once it hits 81? celsius it cut-off fuel at idle.

  19. #19
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    Similar issue and part solution

    I had the same problem, no desired backfiring with vehicle stopped, while working with vehicle moving. Different engine, 2016 3.6L V6 Jeep Wrangler NA, similar backfiring tuning, the following solved it for me:
    Under Engine>Spark>Advance>MinimumSpark modify the Torque Reduction table similarly to what you did in the Minimum Spark Base Table. Apparently the ECM considers the Torque Reduction table as soon as the car is stopped. This did the trick for me and I get the desired backfiring while stopped/parked/in N/P .

    These are just my thoughts, I hope that above Torque Reduction table *might* help resolve your or somebody else's issue....
    Attached Files Attached Files
    Last edited by SteveDigital; 03-22-2019 at 11:03 PM.

  20. #20
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    Quote Originally Posted by SteveDigital View Post
    I had the same problem, no desired backfiring with vehicle stopped, while working with vehicle moving. Different engine, 2016 3.6L V6 Jeep Wrangler NA, similar backfiring tuning, the following solved it for me:
    Under Engine>Spark>Advance>MinimumSpark modify the Torque Reduction table similarly to what you did in the Minimum Spark Base Table. Apparently the ECM considers the Torque Reduction table as soon as the car is stopped. This did the trick for me and I get the desired backfiring while stopped/parked/in N/P .

    These are just my thoughts, I hope that above Torque Reduction table *might* help resolve your or somebody else's issue....
    Tried the torque reduction didn't help maybe in your case it's a spark related issue but for me it's fuel cut-off,

    Any luck with the others ?