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Thread: High Idle while coasting - Troubleshooting

  1. #1
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    High Idle while coasting - Troubleshooting

    Issue: Netural coasting at any speed, high idle 2K rpms, until a dead stop, idle is back to normal: 650.

    Troubleshooting:

    TPS: switched out with ported TB, checked the % using HP tuners..
    Close: 20%
    Idle: 15%
    High Idle 2K rpms: 22% <---Can happen while turn on of the car, with 176 temp, rev up the engine, rpm will stay stuck above 2K

    TPS: back to stock <<<<------ same as above..

    Fuses: Removed the ECM fuses from the engine bay and below the passenger dash, turn on, reached 176 temp, turn off and then turn on again, ====same issue...

    Pedal: Changed the pedal: same issue
    Why the change: because I saw Pedal 21% and TPS 21% while high idle, either moving or not moving the car...

    ECM: Checked for loose connection <---sucker is very tight..

    Reflashed the ECM using stock configuration, no change, change MAF to stock and Stock TB same issues, Stock MAF with ported TB same issue..

    Check my buddy's corvette: Auto 2007 vette, pedal % and TPS % is the same normal temp, 19% if you want to know..

    Checked for leaks using a smoke machine.. no joy,, no leaks http://www.hptuners.com/forum/images/smilies/crazy.gif

    Changed the PCV plastics to actually vacuum lines, no joy.. covered all vacuum lines using a golf tee.. no joy...

    I have looked everywhere expect for change the ECM... how many of you will change the ECM after everything...

    oooo by the way I have not gone to the dealership to complete the Idle relearn,, that will be monday... i'll let you know what happen...


    If after that does not fix it.. then I have to order an ECM and replaced and reflash it <<<---- I dont think I have to do that.. but I may have tooo

  2. #2
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    Logs and tunes

    Here are the logs and tunes

  3. #3
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    Just for gills and s***s..... does the LS2 have an EGR valve....?????

  4. #4
    Senior Tuner edcmat-l1's Avatar
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    Quote Originally Posted by cmt_cibarra View Post
    Just for gills and s***s..... does the LS2 have an EGR valve....?????
    No. GM hasn't used an EGR on an LS engine since about 1999. In the cars at least. I don't do enough trucks to comment on them confidently.

    EFI specialist
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  5. #5
    Senior Tuner edcmat-l1's Avatar
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    Post a log of it doing it. Hanging at 2000 rpm, and then returning to idle. Include ETC position, RPM, timing, MAF Hz, MAP, dyn air, etc.

    It's not a bad PCM. Replacing it would be a waste of time and money.

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  6. #6
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    OKay I did the log as your requested... thanks for the ECM..

    Therefore the other item will be TAC module.. that also controls the TPS and ETC.. and other sorts..

  7. #7
    Senior Tuner edcmat-l1's Avatar
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    Quote Originally Posted by cmt_cibarra View Post
    OKay I did the log as your requested... thanks for the ECM..

    Therefore the other item will be TAC module.. that also controls the TPS and ETC.. and other sorts..
    The TAC module is integrated into the PCM on the E40s and up. They are not a seperate module like the LS1s.

    I will look at the data log a bit later.

    EFI specialist
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  8. #8
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    Thanks a bunch.. seems to me that I'm getting closer now..

  9. #9
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    okay so it's resloved.. when to the dealership.. and completed a reflash and an update.. works find... so it seems mr computer went into a depression mode..

    i have upload the vcm read.. enjoy....glad to have my daily driver back to normal..

  10. #10
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    ok i went a head and upload my small tune with the update..

    if you have anything else to tell me to tune let me know.. i wont mind the feedback...

    thanks a bunch forum.. you guys have been very helpfull

  11. #11
    Potential Tuner
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    Hello. My 2002 LS1 was doing this. There are half a dozen forum posts that end with "the tuner fixed it" or they don't have a resolution. Not exactly helpful, thus why I'm posting here after 9 years.

    I joined to post what the tuner changed to fix it. They need to alter the Enable and Disable Speeds for the Throttle Cracker Idle settings. In my case, they did this and it didn't work. They then swapped to a new PCM, reflashed with the exact same tune and Walah, it worked! So if the Throttle Cracker settings aren't fixing the problem, it may be something in the PCM and worth trying a second one.