95 1/2 ton 4WD, irregular high idle

My pickup (305ci, tbi) idles high, 1100-1500 rpm, at times. Most often it is ok, and seems ok cold. Changed the idle air control, thought I had it, but the problem came back.
Also inspected for vacuum leaks. Irregular enough that when I have time to work on it, it runs ok. Hard to track down.

My pickup (305ci, tbi) idles high, 1100-1500 rpm, at times. Most often it is ok, and seems ok cold. Changed the idle air control, thought I had it, but the problem came back.
Also inspected for vacuum leaks. Irregular enough that when I have time to work on it, it runs ok. Hard to track down.


replace PCV valve and if the rubber hoses are hard/cracked/collapsing replace all as these hoses get damaged more so than the others. espec. where they connect to intake......

I would also suggest to replace the PCV gromet if it is hard and not sealing well. This made a big difference on my 90 GMC K1500 5.7.

A high idle could be a vacuum leak. The TBI Base gasket was a common issue with the original gaskets. Check the vacuum lines to the MAP sensor. I leak in this line will cause the ECM to think the engine is under load and give the engine more fuel.

A bad engine coolant temp sensor can also cause a high idle. If off enough, it will cause a check engine light.

//2000CAYukon