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High idle after cleaning throttle body.

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by Dantheman96, Jan 23, 2012.

  1. Dantheman96

    Dantheman96 New Member

    96 GMC k1500 Suburban with a 350. I took off my throttle body and cleaned it with carb cleaner. It had about a 1/4 inch of gunk underneath the butterfly. Got it shiny clean. I replaced the throttle body gasket on the intake too. I have 1000 rpms at idle in gear, but when driving, the idle doesn't drop back down right away when I let off the gas. I believe the idle is supposed to be around 800 rpms? Any advice? Thanks.
  2. dsfloyd

    dsfloyd New Member 1000 Posts

    Is it running fine other than high idle? A vacuum leak would usually do the opposite and make it run rougher. Not sure if yours requires it as my 04 truck doesnt but on some vehicles an idle relearn is necessary if you remove the throttle body. that is the same thing that happens in my wifes nissan when I clean the throttle body and its a certain number of timed pedal presses and key turns etc.
  3. Dantheman96

    Dantheman96 New Member


    Thanks for your reply dsfloyd. It runs smooth as glass and there is no vacuum leaks. All I did is clean the throttle body thoroughly. I disconnected the battery for 30 min to clear the code and let the pcm relearn, but with no result. I did however find something interesting. When I wiggle the connections at the pcm, the idle increases alot like there is a loose connection there. It's hard to brake this 5000 pound beast when it's idling high. My brakes were getting hot last night.
  4. murdog94

    murdog94 New Member 1000 Posts

    Carb cleaner is an enemy of the TBI.. but i would actually think that somehing with the IAC, or the TPS is shot. I would start there, and yes i get the giggling wires.. Also i know you only cleaned the TBI, but there is a chance that you have an intake gasket leak as well.
  5. Dantheman96

    Dantheman96 New Member

    Thanks murdog for your reply. I replaced the IAC 2 days ago and replaced the intake gaskets 6 months ago. I sprayed carb cleaner along the intake and the base of the TB to double check. The only thing I haven't replaced is the TPS. That's going to have to wait until payday.
  6. murdog94

    murdog94 New Member 1000 Posts

    I would first trouble shoot it.. you can do a sweep test, that will tell you if it is bad or not.. there is a procedure here on the forum how to do that. Then you arent just throwing parts at it.

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