hi everyone. ive got a '98 4.6L with about 218,000. lately i have been having problems with it randomly idling really high. sometimes it will happen when im driving, other times when im just sitting still. on my way home tonight i was pulling in to my neighborhood and i threw it in neutral and i could tell it was idling really high almost like i was hitting the gas. what could be causing this?

 

First check for any vacuum leaks.

 

did that and i cant find any. i think its the IAC. i just cleaned it but it keeps making this weird humming noise. i think i might just go get a new one

 

That sounds like a typical symptom for a sticky IAC valve. If cleaning didn't help, I'd try changing it out.