I have a 99 4.2 , great truck, but I'm having a problem and I can't seem to figure it out. After driving for a few miles and I take it out of gear 9approaching a stop sign, etc.) the damn thing sounds and acts like it's taking off for flight. Reving very high out of gear. Any ideas ? Thanks

 

sticking IAC valve or sticking throttleplate could cause this. among other things
is the truck still cold when it does this? does it do it every time?
can you get a RPM readings of how high it goes?

 

It doesn't do it cold. Only after I have driven it a few miles. I'm thinking it's the IAC valve. Thanks for the response.

 

Ok, I may have fixed the problem, heavy on may. I unhooked my battery cable last night and I just went and hooked it back up and drove 5 miles. Ran like a top. I hope this cures it. Thanks Mr.B for the response.