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TBI high idle... HELP!!

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Blazinaire, Jun 4, 2003.

  1. Blazinaire

    Blazinaire 1/2 ton status

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    '87 k5 with TBI 350, 190k miles, new O2 sensor, idle air controller (IAC) works properly, computer doesn't throw any codes... What could it be? Idles around 1300-1400 rpm and has been for at least 10 months /forums/images/graemlins/shocked.gif I was told that the throttle positioning sensor (TPS) could have an effect on the idle if it was really screwed up, but wouldn't it throw a code? I know didly squat when it comes to electonics so please explain in lamens terms /forums/images/graemlins/thumb.gif Thanks in advance for any /forums/images/graemlins/1zhelp.gif
     
  2. fortcollinsram

    fortcollinsram 1/2 ton status

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    check the TPS...it is infront of the IAC on the TB...It should be around .5v at idle and around 4.5v at WOT...Also check MAP sensor and CTS....

    Chris
     
  3. TopOff

    TopOff 1/2 ton status

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    Vaccuum leak. I had the same problem, except mine idled ~2000!

    Good luck.
     
  4. rampage

    rampage 1/2 ton status

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    Mine idled at 1400 and wouldn't pass emissions. Turned out to be the TBI gasket was leaking. Spray some carb cleaner around the gasket and see if the rpms increase slightly.
     
  5. MousePowrd

    MousePowrd 1/2 ton status

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    Check all vacuum lines. My truck has 100k and they were all bad, I guarantee yours are worthless.

    Change the TPS. Only $20 at Autozone. I just put one in mine because intermittently My idle would go to 1100 in gear, then 500. It fixed the problem.

    If those dont work, check the TB gasket as mentioned above, and the intake manifold gasket. Spray carb cleaner around the gaskets with the engine idling and if there is a leak, the idle will change when you hit the leak with the spray.
     

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