high idle

Discussion in 'General Chevy & GM Tech Questions' started by jeroen, Feb 5, 2010.

  1. jeroen

    jeroen New Member

    hi guys,
    i'm the owner of a Suburban with a 454QI TBI engine.
    the problem is that when i'm slowing down to stop from speed, the engine stays on high idle.
    when i go to nutral the engine go's to normal idle.
    excuse my english. i'm from holland, europe.
    Last edited: Feb 5, 2010
  2. Wpowell

    Wpowell Member

    I strongly suggest that you go on line and get a Helms Driveability and Emissions Service Manual for your vehicle. I bought one for my 87 350 pu and it walks you through all the individual diagnostics and troubleshooting for your engine.

    On mine truck there is several things that jump out at me on your question.
    • The IAC (Idle Air Control) valve in the throttle body could be malfunctioning
    • TPS and EMC could be part of the issue.
    • The Electronic Pick Up in the distributor could be sending a false RPM to the EMC and it then is adjusting the idle up as well.
    Regardless the Helms manual will keep you straight and walk you through it step by step.
  3. jeroen

    jeroen New Member

    thank you for your answer, i will check those 3 points.
  4. jeroen

    jeroen New Member

    :great:thank you for your answer, i will check those 3 points.
    i will search the internet for that manual and order it.

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