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high idle problems

Discussion in 'Chevy C/K Truck Forum' started by okysmokey911, Jul 24, 2010.

  1. okysmokey911

    okysmokey911 Rockstar 100 Posts

    I have been having a problem with my truck's idle. Lately the idle, when I first start the truck, will go up to about 1500 rpms and stay there until I kill the truck and start it again then the idle goes to about 900 to 1000 where I have it set at. I have the holley 502-9 throttle body on it with the adjustable tps, but even playing with the adjustable tps I still cant fix this problem. Every once in a while while I am driving the idle will rise and stay at 1500 to 2000 rpms. Any thoughts on what might be causing this?

    ---------- Post added at 01:52 PM ---------- Previous post was at 01:50 PM ----------

    my truck is a 93 k1500 5spd with a newly rebuilt 5.7 350 in it
  2. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    Idle air control valve is what sounds like your problem. The servo in the IAC is either bad or stuck from carbon. Also you might be suffering from improperly installed Intake gaskets. Or a vaccum leak.
  3. okysmokey911

    okysmokey911 Rockstar 100 Posts

    I guess it could be the iac but it is practically brand new and the intake manifold gaskets are good... could it possibly be the tps sensor? mine is adjustable so that you can set the idle where you want it and today when I tried to adjust it, it made a weird noise and would not raise or lower the idle soo I am thinking it could be faulty, but the tps is only about a year old or so. I noticed that while the truck was just sitting the idle would just raise itself a couple thousand rpms without pressing the gas.... I cant figure this out.
  4. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    Could be the TPS.... Im not to sure if you do a sweep test with an adjustable TPS the same as a regular TPS? If so i would try a sweep test.. And i realize the IAC is new i was also just talking about a piece of carbon or something can get stuck, but it seems that raising as much as you are talking about is related to the TPS,Computer...
  5. okysmokey911

    okysmokey911 Rockstar 100 Posts

    Yeah I was also wondering the same thing if a regular tps would work rather than putting an adjustable one back on there because I cant even find this tps from the holley website. I am hoping that the ecu is not messing up. Could timing play a factor at all. I am thinking that it wouldnt because the range at which the idle increases seems to be way too big for it to be timing. I guess Ill just go get a regular tps and see what happens.

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