1990 cheyenne idles waaaaaaaay too fast

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  #1  
Old 06-29-12, 06:27 PM
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1990 cheyenne idles waaaaaaaay too fast

otherwise it runs great. there are no vacuum leaks. i have replaced the IACV, but it did not touch the problem. even after the engine if fully warm, idle is waaay fast. could it be the throttle position sensor, and how could i test this?
 
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Old 06-30-12, 05:11 AM
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Possibly the TPS. Is it carburetted or TBI? How did you check for vacuum leaks? Did you replace the PCV valve? HOw 'bout the EGR sensor?
 
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Old 06-30-12, 05:37 AM
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I second the question --"how was the vacuum checked". I would suggest a vacuum gauge.
A vacuum gauge is a very useful tool if you learn how to read it and diagnose the problem. Many times, this old tool has found problems high-tec equipment missed
If a vacuum leak is discovered, or suspected, I have found that a simple water mist sprayed from a bottle, will give clean results.
 
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Old 07-04-12, 08:41 PM
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i think i found the problem. when i pulled the pcv out of the valve cover, and then covered the opening of the pcv, the idle dropped right to normal, instantly. sooo, i bought a new $2.99 pcv and installed it. idles great. i never would have suspected that a pcv problem could cause an engine to idle at high speed. i do not have a speedo, but i suspect it was idleing at about 3k before i replaced the pcv. thanks for the responses.
 
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