Sounds like a sticking throttle cable or cruise malfunction as has been said before. There is only one major route for air to get from the intake to the plenum (and into the cyls) and that's past the throttle plate. The throttle on these trucks is not more complicated that a cable is pulled to open it, and a spring shuts it. Cruise can also actuate it, and that system has a lot more possibilities for faults.


The engine would start to run badly as un-metered air would be sucked in through the screw hole. That said, I've never had cause to remove the idle screw to see how large the vacuum leak would be.

 

The throttle cable isnt hooked up that was one of the first things i unhooked, and it doesnt have cruise control. Its just the standard 4x4 pickup truck with ac and pwr steering and thats it.

 

what about timing, chain possibly jump or maybe the distributer is a little lose causing high idle, put you engine at top dead center and make sure rotor is pointing at number 1
There was a kid in my shop class pulled his car in no problems went to leave and it would not start, some how the dis came lose and turned just enough while driving it that is would run but not restart