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Thread: gmpp ls3 high idle

  1. #1
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    gmpp ls3 high idle

    New to gen4 ecm cant get the thing to idle below 850 rpms. Its all stock straight from the crate runs good just want it to idle around 700.
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  2. #2
    looks good. check for air leak. added air can raise the idle

  3. #3
    Ive run in to this before with the GMPP controller as well as others on here, best I can conclude is its some sort or hardware or software issue that we don't know about yet. You can log desired idle speed and it will reflect what you have put in your idle tables but still idles high(annoying). Idle airflow min seems to have almost no affect on blade position also, like the TAC has a mind of its own lol. You will also notice the over/under spark tables are not using timing to lower the idle speed, typically on a 38/67 if TPS is open too much timing will be very low and its not. Maybe there is a table we don't have access to and support might know more about this.
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  4. #4
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    This shouldn't be an unfixable issue. Like I said to the OP in this other thread, start with a good log with the right PIDs. There are other tables besides the min air tables that control the blade position obviously. Let's see what the logs show first.

    https://www.hptuners.com/forum/showt...Throttle-Decay

    LS3 Channel gmtech.Channels.xml

    LS3 Charts gmtech.Charts.xml

    LS3 layout gmtech.Layout.xml
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  5. #5
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    Quote Originally Posted by gmtech16450yz View Post
    This shouldn't be an unfixable issue. Like I said to the OP in this other thread, start with a good log with the right PIDs. There are other tables besides the min air tables that control the blade position obviously. Let's see what the logs show first.

    https://www.hptuners.com/forum/showt...Throttle-Decay

    LS3 Channel gmtech.Channels.xml

    LS3 Charts gmtech.Charts.xml

    LS3 layout gmtech.Layout.xml

    Any Progress on this issue?

    I have a LS376/525 and i have just swapped the cam for to the standard LS3. However after allot of work remapping for the CAM i cant get it to idle below 950 rpm....

    When i select drive (6l80e) and start rolling forward the idle speed drops to the desired 550-600 rpm but as soon as i select park it jumps back to 950 rpm.

    Is there something built into the GMPP ECU that cannot be modified using HP Tuners?

  6. #6
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    I've made some progress for those with GMPP engines with high idle speeds!

    Ive just downloaded a gmpp LS376/430 file from HP tuners - Tune repository - i did a slightly unorthodox tune because I wrote the entire file to my ECU.

    (my ECU is a LS376/525 and ive swapped the LS3 525hp hot cam for the standard 430 hp gmpp LS3 cam to improve fuel economy, reduced noise, 6L80e is no longer trying to pull - drag the car forward at idle in drive).

    The idle speed is now sitting at 550 rpm instead of 950 rpm.

    Im currently working on Fuel/Spark/Air ratios etc, so that it's setup for my engine configuration.

  7. #7
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    Quote Originally Posted by chris2abel View Post
    I've made some progress for those with GMPP engines with high idle speeds!

    Ive just downloaded a gmpp LS376/430 file from HP tuners - Tune repository - i did a slightly unorthodox tune because I wrote the entire file to my ECU.

    (my ECU is a LS376/525 and ive swapped the LS3 525hp hot cam for the standard 430 hp gmpp LS3 cam to improve fuel economy, reduced noise, 6L80e is no longer trying to pull - drag the car forward at idle in drive).

    The idle speed is now sitting at 550 rpm instead of 950 rpm.

    Im currently working on Fuel/Spark/Air ratios etc, so that it's setup for my engine configuration.

    I'm having this same problem. Exactly which tune is it in the repository? thanks

  8. #8
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    Quote Originally Posted by chris2abel View Post
    I've made some progress for those with GMPP engines with high idle speeds!

    Ive just downloaded a gmpp LS376/430 file from HP tuners - Tune repository - i did a slightly unorthodox tune because I wrote the entire file to my ECU.

    (my ECU is a LS376/525 and ive swapped the LS3 525hp hot cam for the standard 430 hp gmpp LS3 cam to improve fuel economy, reduced noise, 6L80e is no longer trying to pull - drag the car forward at idle in drive).

    The idle speed is now sitting at 550 rpm instead of 950 rpm.

    Im currently working on Fuel/Spark/Air ratios etc, so that it's setup for my engine configuration.
    Thank you!

    I did as you suggested; put GMPP 430 tune on a GMPP 525 controller with write entire. Idle rpm adjustments do work now nicely.

  9. #9
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    Cool info. I?ll try this on the LS3/480 I worked on this month after the customer moves his air intake to a cooler air location.
    Ron

  10. #10
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    Quote Originally Posted by RonSSnova View Post
    Cool info. I?ll try this on the LS3/480 I worked on this month after the customer moves his air intake to a cooler air location.
    Ron
    Please do so. The GMPP LS3 file is in the tune repository. Just search "GMPP" and you'll find it.

    Just don't leave the stock 550 rpm for the idle target with 525 hp LS camshaft...