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TBI Idle Problem

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by tom, Aug 15, 2001.

  1. tom

    tom 1/2 ton status

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    Our '90 TBI blazer runs great, except that the computer won't let the RPM drop rapidly when the gas pedal is released. This is a real pain with the stick shift (SM465). It makes shifts slower and rougher than normal. Is there a way to correct this? My guess is that this feature is part of the smog control system. The TBI is better than the quadrajet in every way except for this annoying characteristic. Thanks in advance for any help or ideas.
     
  2. Bubba Ray Boudreaux

    Bubba Ray Boudreaux 1 ton status

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    Gas pedal released? Okay. Anyway, sounds like maybe the TBI gasket is bad. Easy way to check is spraying carb cleaner (correct me if I'm wrong, can't remember what was used) around the TBI and this will find the leak if there is one. Gasket kits are cheap and easy to replace.

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  3. rampage

    rampage 1/2 ton status

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    I had a high revving problem also that kept me from passing smog. They wanted 400 bucks to diagnos and fix the problem. Turned out to be a leaking TBI gasket. Like was mentioned, use carb cleaner and listen for the RPMs to jump a little. It's easy and cheap to check for this and the repair (gasket) is about $10 and about an hour to do. Check this fist.
     
  4. 90idahoblazer

    90idahoblazer 1/2 ton status

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    Do you spray the carb cleaner around the base of the Gasket...Also have any of you adjusted the idle on a TBI..???or is it computer controlled only
     
  5. Twiz

    Twiz 1/2 ton status

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    TBI with high ildle concerns;
    -Check for TBI gasket leaks, very common problem. way-outside (fumes will bring tears to your eyes), spray the base of the TBI, engine idle should increase if there is a leak.
    -Check for throttle shaft bore wear. Grab the throttle shaft and wiggle it, there should only be rotational movement and no "slop" in the shaft. Also, spary carb cleaner around the shaft will also help find the vacume leak.
    -Check throttle bores for contamination, use carb spray to clear and clean.
    (there are someother possible causes to engine idle concerns, I have found the list above to be the most common)

    TBI idle sys is controlled by the IAC (Idle air controler) and ECM. Do not atempt to adj engine idle externaly.

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  6. jarheadk5

    jarheadk5 1/2 ton status

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    That's an emissions-control feature programmed into the computer. Do you have any other engine mods? If so, maybe <a target="_blank" href=http://www.fastchip.com>www.fastchip.com</a> can burn you a new chip that doesn't have that feature.

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