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TBI Idle too high??

Discussion in 'The Garage' started by 4xcrazy, Oct 14, 2005.

  1. 4xcrazy

    4xcrazy 3/4 ton status

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    Aight, here's the deal, i AM mechanically inclined, can work on a motor pretty well and whatnot, but this computer controlled stuff still has it's points where i just don't know enough about it to do certain things,,,make sense?

    I am wondering, from any of the TBI tech's out there, how would i go about turning the idle down just a tad on the Burb,,i start it, it idles up pretty high, then as it run, the computer does it's thing and turns it down a bit,,,but i just don't think it's enough.

    It does turn down a bit more after it's been in gear for about 10 seconds, but as soon as i throw it back into park, it wants to idle up again.

    Not sure what the rpm's are as of yet, haven't gotten around to hooking up a tach yet.

    Any ideas or hints?

    everything BTW is all stock......nothing aftermarket,,,well except when some sensore were replaced a few years back,,, :doah:
     
  2. blazerguy 90

    blazerguy 90 1/2 ton status

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    Try removing the IAC (idle air control) and cleaning it and the area were it screws into the TBI, or better yet, remove the TBI and give it a good cleaning and replace the base gasket, they can go bad and cause a vacuum leak and high idle. when I removed my TBI and gave it a good cleaning it made a big difference.
     
  3. ryoken

    ryoken Puppy Fabricator Premium Member GMOTM Winner

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    loose throttle shaft and vacuum leaks will cause high idle.

    heres how you can adjust idle tho if everything looks good..Take a paper clip and jump the ALDL in the 'A' and 'B' pins.

    Turn on the ignition, but don't start the engine. Wait 30 seconds. Now, go remove the connector from the IAC.

    Start engine. You are now going to adjust "minimum air". There is a Torx screw on the side of the throttle body. This is what needs to be turned to adjust minimum air, or more commonly known as "idle speed". It comes from the factory with a protective metal cap over it. If the cap is still there, use a small punch to knock it out. Set the idle speed to 450 rpm, rotating the Torx screw clockwise to raise rpm, and counter-clockwise to lower rpm. Once the idle rpm is set, turn off the engine.

    Re-connect the connector onto the IAC. Start engine. Idle speed is now once again governed by the ECM, but your idle should be smooth and steady, approximately 600 rpm in Drive (for unmodified cars).

    If you set an SES light by having the IAC disconnected, then after shutting down the engine disconnect the negative battery terminal. Wait 5 minutes. This will clear the ECM of all trouble codes. Re-connect the battery and drive the car for 20 minutes to allow the ECM to relearn your driving style.
     
  4. southernspeed

    southernspeed 1/2 ton status GMOTM Winner

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    I concur!
     
  5. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    The above is correct for setting minimum air less one detail, after you unplug the IAC, make sure to pull the paperclip out before you start the engine, or else it'll run in limp mode :)
     
  6. ryoken

    ryoken Puppy Fabricator Premium Member GMOTM Winner

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    hmmm... thats straight off thirdgen's faq... surprised that wasn't mentioned... :confused:
     
  7. sweetk30

    sweetk30 professional hooker Premium Member

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    like all others . vac leaks. base gaskets vary comon problem. with it running spry some brake cleaner around the base gasket and other areas if idea jumps then you have found the leak.
     
  8. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    http://www.thirdgen.org/techbb2/showthread.php?s=&threadid=272791

    Here is a thread from thirdgen that disscusses this :) Also has some more very indepth detail on exactly what you are doing when you set minimum air, with pictures :)
     
  9. ryoken

    ryoken Puppy Fabricator Premium Member GMOTM Winner

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    hmmm... TPI section... no wonder i missed it.... :doah:

    thanks :D
     
  10. unclematty

    unclematty 1/2 ton status

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    bet a donut theres a vacumm leak somewhere :D
     
  11. 4xcrazy

    4xcrazy 3/4 ton status

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    i'll check some things out soon, but just so you all know, it's not super high, and it's not surging at all, it is manageable, drivable, just seems alittle too high compared to the other vehicles i have owned. guess i really need to get a tach hooked up to it to see exactly what it's doing.
     

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