I have a 2001 F150 4x4 automatic with 5.4 V8 that lately has been acting up. When I start the engine cold it revs to a little over 2000 RPM and then settles down to a normal idle; never used to rev that high. I've also noticed that when it is settling in to a normal idle range if I change the HVAC function (like from Panel to Floor) it jumps up about 500 RPM and then back down. I'm also seeing RPM surge when stopped in gear if the HVAC is set to a function that engages the AC, like one of the defrost settings. With AC on, it will surge from 600 to around 850 and back, with AC off it stays steady at 600. Any advice on where to start troubleshooting?

Thanks.

Eric

 

Start with the IAC. Remove it and clean or replace it.