High idle on 5.7L Vortec

Discussion in 'General Tech' started by RKBJR, Jun 25, 2006.

  1. RKBJR

    RKBJR Active Member

    Joined:
    Mar 21, 2005
    Location:
    Roxboro, NC
    I'm getting a high idle on the Vortec 350 in my Cruiser. It idles like it should when the engine is cold. Once it warms up to normal operating temperature, it revs higher at idle. Anyone have this problem before?

    R.K.
     
  2. Blkvoodoo

    Blkvoodoo Letting the smoke out Moderator

    Joined:
    Mar 16, 2005
    Location:
    Archer Lodge
    More than likely a vacuum leak. intake gaskets are a common failure on those engines. could be a vacuum line of fitting cracked.

    spray it down with brake or carb cleaner (use the straw o the spray nozzle) following intake at head, around the thottle body and anything else that might could leak air.
     
  3. RKBJR

    RKBJR Active Member

    Joined:
    Mar 21, 2005
    Location:
    Roxboro, NC
    I just had the intake gaskets replaced. I had the high idle problem before and after having them replaced.
     
  4. Rich

    Rich Asshole at large

    Joined:
    Mar 17, 2005
    Location:
    Central PA
    It could very well be the computer.. If you're gonna run some whiz-bang high-tech motor like that, you'd be very good to have a tool that can monitor the sensors and ECU output real-time for diagnosis. :flipoff2:

    There's a ton of things that could make the idle high.. and a BUNCH of sensors.. Off the top of my head - thinks A/C is engaged, thinks it's constantly cold, etc..
     
  5. BIGWOODY

    BIGWOODY Well-Known Member

    Joined:
    Mar 21, 2005
    Location:
    Thomasville
    do you have an OBD2 connector on your harness?...the guy who did mine for the LS1 left the OBD2 connector on it and I can still monitor all the engine stuff, all you would need is a cheap scanner.
     
  6. RKBJR

    RKBJR Active Member

    Joined:
    Mar 21, 2005
    Location:
    Roxboro, NC
    We fixed one small vacuum leak, but that wasn't the problem. The throttle cable was tighter than it should be. We modified the bracket to give it some slack, but it still idles a little high when warm. It has a slight surge, almost like it wants to idle back down, but then kicks up again. When I turn the engine off, and then back on, it idles fine. I do have a diagnostic port on the Painless harness, so I will try to pull some codes tomorrow.

    R.K.
     
  7. 87bazuka

    87bazuka New Member

    Joined:
    Jun 22, 2006
    Location:
    Moncure
    Try taking off your air induction, and look on the inside of the throttle body. There should be a little hole off to the side, spray that hole with Throttle and choke cleaner and spray your throttle body down real good. Some times cabon builds up in there and make the Throttle position sensor act funny.-David
     
  8. greg slade

    greg slade The Moderated

    Joined:
    Mar 21, 2005
    Location:
    timberlake
    R.K. , It's most likely the coolant temperature sensor (not sender) for the computer if it is not a vacuum leak. Very common problem for the SBC F.I. swap that sees some engine washing occasionally. Mine went bad at tellico at the dixie last year, the idle will eventually keep creeping up until its too high to drive with.

    Hope It Helps, Greg
     
  9. RKBJR

    RKBJR Active Member

    Joined:
    Mar 21, 2005
    Location:
    Roxboro, NC
    Replaced the coolant temperature sensor today, seems to have helped some. But it still idles higher than it should.

    Gonna clean out the throttle body next. Any other suggestions?
     

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