idle was bouncing up and down after i drove to work today and was in park. Replaced iac few months back. Any thing else i should check for. I have no codes. iac i replaced wasnt a dealer part. maybe vacuum leak?

 

Usually that's a vacuum leak..... but, could be just a slow to react IAC as well. My truck still does it once in a while, but, it isn't consistent, might do it three days in a row, and then, not again for a month......

 

Not to get too far away from the original thread but ages and ages ago I was stopped in the left turn lane at a red light in my '91 Chevy Blazer, it started to idle rather strange, and suddenly, with the brakes completely depressed, the vehicle started to lurch forward with the crazy idle, it probably moved up 2' before it stopped.

Crazy....

 

funny you say that, jumped in truck after work and it wasnt doing it again, drove 20 miles nothing... went ahead and bought a different brand iac as a backup. Wanted to get one from dealer, but they were *** hats. Couldnt hear any vacuum leaks but i might get in there and check the lines, but i did however do an ECU reset with my tuner before i left work, and it was fine. so it seems like the current IAC might be just crapping slowly.