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Thread: TBI with High Idle in PARK

  1. #16
    Fuel Injected! brian617's Avatar
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    Quote Originally Posted by stew86MCSS396 View Post
    In post #1 you said tuner set idle target to 600 rpms. As already mentioned twice, You need to set minimum idle 125 rpms below 600 rpms.

    I think everyone is getting confused. If he had the minimum idle set too high the IAC would zero out. You have to read the original post a few times to understand what he did.

    Two things I suspect either the IAC motor is bad and giving a false step reading (the IAC position is 44), or there is another parameter that is causing the high idle. This is the point when a data log and a .bin file is a must.
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    Quote Originally Posted by brian617 View Post
    I think everyone is getting confused. If he had the minimum idle set too high the IAC would zero out. You have to read the original post a few times to understand what he did.

    Two things I suspect either the IAC motor is bad and giving a false step reading (the IAC position is 44), or there is another parameter that is causing the high idle. This is the point when a data log and a .bin file is a must.
    The confusion is "minimum idle" - when you set minimum idle you set it by adjusting idle with the throttle blade stop screw (with IAC bypassed) to 125RPm below target idle. If you don't you'll burn up the stepper motor in the IAC since the ECM will continuously try to close the pintle more to reach "target idle" speed. The IAC can not zero out the idle if the blade shaft stop is holding it open.

  3. #18
    Fuel Injected! brian617's Avatar
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    Quote Originally Posted by PlayingWithTBI View Post
    ECM will continuously try to close the pintle more to reach "target idle" speed. The IAC can not zero out the idle if the blade shaft stop is holding it open.
    Still confused. If the minimum idle were too high the ECM would drive the IAC pintle to 0 steps and be unable to lower the idle further. However his IAC count is 44, way higher than I shoot for when setting.

    I dont bother with minimum idle spec. I want my TPS voltage between .50 and .65 and I want my IAC steps around 15 counts on a hot engine no load.
    89 K1500 Scottsdale 5.7L 5spd 3:42 RamJet cam Dart iron TBI heads 427 PCM swap
    95 C2500 Cheyenne 6.5L turbo diesel 4L80e 4:10 DB2-4911 Manual pump conversion 0411 PCM trans control 2Bar COS
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  4. #19
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    Quote Originally Posted by JJK10 View Post
    I can get it to idle slower in park is to jumper the A&B pin and force the IAC closed then unplug it and adjust the throttle blades open and she idles nicely at 700 rpms.
    Quote Originally Posted by JJK10 View Post
    I have followed the base idle setup procedure but as soon as I plug the IAC back in it opens up and the Idle goes to 850
    Read these two sentences separate. Not as one.
    89 K1500 Scottsdale 5.7L 5spd 3:42 RamJet cam Dart iron TBI heads 427 PCM swap
    95 C2500 Cheyenne 6.5L turbo diesel 4L80e 4:10 DB2-4911 Manual pump conversion 0411 PCM trans control 2Bar COS
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  5. #20
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    Quote Originally Posted by brian617 View Post
    Still confused. If the minimum idle were too high the ECM would drive the IAC pintle to 0 steps and be unable to lower the idle further. However his IAC count is 44, way higher than I shoot for when setting.
    If the minimum idle wasn't set 1st the IAC may be already bad.

    I dont bother with minimum idle spec.
    You may get bit if you don't...

  6. #21
    Fuel Injected! brian617's Avatar
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    Quote Originally Posted by PlayingWithTBI View Post
    You may get bit if you don't...
    How?
    89 K1500 Scottsdale 5.7L 5spd 3:42 RamJet cam Dart iron TBI heads 427 PCM swap
    95 C2500 Cheyenne 6.5L turbo diesel 4L80e 4:10 DB2-4911 Manual pump conversion 0411 PCM trans control 2Bar COS
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  7. #22
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    Read these two sentences separate. Not as one.
    OK, my bad - I missed that.

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    Thanks everyone! I'm working with Old School Efi and I believe he is going to try to burn a Manual chip to see if that might bring the in PARK idle down. Any other ideas would be welcome! long story short the wiring and the tuning approach (until now, David is trying a manual bin) are the only two things that haven't changed and at the end of the day how can you have AIC counts in the 50's and at 850 rpms in park? Also worth noted that this engine was transplants from a donor truck by previous owner. Any help would be great. Thank you!

  9. #24
    Super Moderator dave w's Avatar
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    Manual Trans .bin attached.

    dave w
    Attached Files Attached Files

  10. #25
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    Quote Originally Posted by JJK10 View Post
    how can you have AIC counts in the 50's and at 850 rpms in park?
    Something is driving the IAC to 50 counts, the result is an idle of 850 rpm.

    Your IAC at hot idle, no load should be around 15 counts.

    With no .bin file or data log the rest of us can't help much.

    I'm sure Dave will get it sorted out.
    89 K1500 Scottsdale 5.7L 5spd 3:42 RamJet cam Dart iron TBI heads 427 PCM swap
    95 C2500 Cheyenne 6.5L turbo diesel 4L80e 4:10 DB2-4911 Manual pump conversion 0411 PCM trans control 2Bar COS
    05 Outback XT 2.5L turbo gas auto

  11. #26
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    Quote Originally Posted by brian617 View Post
    Something is driving the IAC to 50 counts, the result is an idle of 850 rpm.

    Your IAC at hot idle, no load should be around 15 counts.

    With no .bin file or data log the rest of us can't help much.

    I'm sure Dave will get it sorted out.
    Dave is working on it! but I cant help but think something in the wiring is causing this high idle.... had the same issue with the L05 engine I removed. Maybe if Dave gets time he can post my last log... it might make for some fun discussion. Thanks Brian617

  12. #27
    Super Moderator dave w's Avatar
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    Log file attached.

    dave w
    Attached Files Attached Files

  13. #28
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    Quote Originally Posted by dave w View Post
    Log file attached.

    dave w
    Thanks Dave!

  14. #29
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    HELP!
    After nearly a year of working on and off on this HIGH idle in park.... its still there! I've tried different computers, different throttle bodies, different chips, different tuners and still no luck. My next try is to start looking into the wiring. Remember from my previous posts that this issue has been there every since I got the truck. The PO was the guy that installed the harness and dropped in the TBI engine from a donor truck. At the end of the day how can the engine idle high and still have IAC counts in the 50's? It seems that the IAC wiring is bad or something is tell the engine to idle at 900, the computer. Please if anyone has any ideas I would be so grateful. Thank you, Jason

  15. #30
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    is this vehicle still tbi? if so don't worry about setting base idle by jumpering the iac closed. set the the base idle screw so IAC counts are 5-15 with engine hot. is the throttle body the same before new engine? has the throttle shaft been bushed? I have not come across a TBI unit in the last 10 years that DOESN'T need to be bushed. a worn throttle shaft can make idle untamable.

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