I'm having trouble with the idle on my 91 22re. I think its the Idle control valve under the throttle body. The truck starts and runs fine, but after afew minutes of running the idle rev's up and down.

The TPS settings are all correct when checking with a volt meter.

But I have the idle speed screw turned all the way down just to keep the idle at its lowest speed. If I adjust the screw, the idle goes up, but still continuously rev's up and down.

If I drive the truck, and put a load on the engine, the idle goes down, but once I push the clutch in the idle goes back up and down.

Do you guys think I have a vacuum leak or is the Idle control valve bad or dirty ?

 

I think your on the right track with the ICV. If it were a vacuum leak then it would be a constant high no fluctuation.