Truck: 1995 Chevy C1500 2wd V6 4.3

Problem: First off, the truck RUNS great. But if i put it in park or neutral after driving around town for a couple minutes it idles Up AnD dOwN; between 600-900 RPMS (almost idles as if you cut the A/C on and off quickly) but DOES NOT do this when the truck is in gear and at a stop OR is in park with the A/C on.

The ECM is giving me CODE 35. and it will ONLY display it under the condition that the truck is in park with the A/C off.

OTHERWISE with the A/C ON it idles right at 600-700 PERFECT

{Ive replaced the IAC valve and the IAC valve harness}

Has anyone EVER had anything happen like this?

Its just real aggravating and i HATE seeing the check engine light...

Thanks guys

-Nate

 

Ours idled all special like that here and there and sometimes would shut off when backing up. Sitting in part it would rev and rev and rev. Not real high but sounded like it was trying to shut off and would rev at the last second to keep "alive." Just so happened to know a guy who had a throttle body to try and it runs like brand new now. My husband took the broke one apart and there was carbon build up that was causing it to stick (which made it have to rev to open it) and also there was a lot of "play" in the gears. (which was causing it to have to rev more before it was reacting and working the little "door") If this doesn't make sense I can have my husband get on here tonight to explain more. Good luck!