I need some input on this. I have a 1997 F150 4.6 4x4 auto and when I start after sitting for a few hoursthe rpms are at about at 1000 when the truck is running I know this is normal because the engine is cooled off a little. to get back to the point the pms are at 1000 and all of a sudden it jumps to about 1500 and then comes back down. When the truck is warm it doesn't do it at all. I'm wondering if the IAC has anything to do with it. Any input would be great. The truck runs great it just annoys the heck out of me that it is doing this.

 

Typically the IAC is the first item to check for idle problems. Best thing to start with is to pull the IAC, clean it, and try again. If it helps, then replace it. Cleaning is only a temporary fix and will only last about 5min to possibly a couple of months depending on how bad it is.