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TBI over-revving when cold

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by smack, Mar 12, 2002.

  1. smack

    smack 1/2 ton status

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    '87 350 TBI 4-spd, no error codes. I seem to have a problem with the engine over-revving until it warms up. If you put the clutch in and rev the engine it takes FOREVER for it to wind back down and actually revs higher between shifts. This is a real problem when driving because I have to shift fast to prevent it from over-reving while switching gears. Could this be an EGR valve problem? The strange thing is that even when I physically pull back the throttle it's still over-reving.
    Hmm??
    Thanks in advance.
     
  2. smack

    smack 1/2 ton status

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    Still looking for any responses -- especially from those crazy TBI experts out there!!! Help!!
     
  3. realsquash

    realsquash 1/2 ton status

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    Either you have icing on the throttle blades and they are sticking open or your IAC motor is slow/gummed up.

    Squash
     
  4. smack

    smack 1/2 ton status

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    Thanks for the response. The IAC, that's that thingy in the intake tube that runs off the flex tube from the exhaust manifold right? Might be good reason to finally remove that damn thing, eh?
     
  5. BurbinOR

    BurbinOR 3/4 ton status

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  6. BurbinOR

    BurbinOR 3/4 ton status

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    By the way, the IAC is screwed into and is at the bottom of your throttle body..............look at http://www.thirdgen.org for pics of locations.
     
  7. TopOff

    TopOff 1/2 ton status

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    Vaccum leak...
     
  8. Take some carb cleaner and spray around the base of the TBI and see if the rpms change. It definitely sounds like you have a vacuum leak due to a bad TBI base gasket. I had to replace a few of them on GM trucks when I worked as a auto technician at a shop.

    Later,
    Doug
     
  9. smack

    smack 1/2 ton status

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    Seems like the ThirdGen site talks about adjusting the IAC and not actually cleaning it. Think it should just be replaced??
     
  10. BurbinOR

    BurbinOR 3/4 ton status

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    Sorry, thought that article covered how to remove it and clean it............look around on the site, there IS a comprehensive procedure to removing the shaft and cleaning/lubing it.
     
  11. smack

    smack 1/2 ton status

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    Thanks, I'll check it out. Ever done any of those mods on the site/?
     
  12. BurbinOR

    BurbinOR 3/4 ton status

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    I wrote the TPI injector swap article, I did the IAC removal/cleaning, TPS mods, and many other tweaks, etc. Good site to read and learn on............../forums/images/icons/laugh.gif
     
  13. smack

    smack 1/2 ton status

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    Yeah, that is a great site, if ever I get time I'd like to try out some of the mods.
     

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