My 95 Jimmy with 4.3 has suddenly started to idle very high when you start it up, check engine light comes on. Let it rest for awhile and restart all is well, drive for a while check engine light goes off. All goes well for awhile and I repeat the above. I'm thinking some kind of sensor or ?????

It sounds like there may be a problem with the IAC motor or its wiring, but guesses can get expensive. What codes(s) are in memory? Autozone and Advance Auto Parts will check the codes at no charge. Write down any/all codes that are in memory and post the them here.

Thanks for the heads up on this one. From reading about it, sounds like you've hit the nail on the head. I'd like to take it out and clean it up. Where is it located? I assume it's near the throttle body? Is there a link to a picture, thanks again.

It's located on the throttle body. There is one electrical connector and two screws, then it just slides out. Do not move the pintle, (valve) by hand. The worm gear becomes brittle and will break. Clean the pintle, seat, and passages. Do not reuse the old "O" ring, replace it with a fuel rated "O" ring.

I took it our and cleaned it up. Started the car and all was perfect and idled right, but check engine light still on, as I went for a 10 minute drive. I was happy as I pulled into the driveway and put it into park, then bingo, high rev's back and check engine light still on. I'm going to have to take it into the shop on Monday and see what's up. Maybe the Idle Control Valve is shot, and the cleaning didn't help or ??????
Thanks again for trying to help. I'll report back when I find out the answer so it might help others in the future.

Don't give up so quickly. As I mentioned earlier, it was a guess, there still may be a problem with the IAC, or the wiring. Find out what codes are in memory, post them here and we'll continue with the diagnosis.

Here's the latest, it was checked out and scanned for codes it came up with, throttle position sensor, it was running at 5 volts just idling. So I'll be replacing it tomorrow when I can get the part. Sure hope this is it.

At idle the throttle position sensor voltage should be around .6 volts. At wide open throttle, voltage should be near 5 volts. Definitely a problem with the TPS or its circuit.

Bought a new TPS this morning, dropped it in....all is well once again with my Jimmy. Thanks again for your responses and idea's.

Glad you got her running again.