Another thought. Look inside the throttle body (the IAC is attached to the top of it) and look at the input from the EGR valve. It's on the right side of the throttle body as you are looking into the throttle body. Might need a dentist mirror to look in the EGR valve input as it is curved...
Just a quick lesson learned. I was replacing the rear door striker bolts in my 2002 Sport Trac when the nut plate in the door frame fell from its slot into the body panel cavity. Argh!! Turns out it was easy to retrieve and reset into its slot. Access to the interior of that body panel is...
I had an intermittant rough idle after the engine was warm. IAC and PCV checked good. Ended up being some very apparent carbon buildup at the end of the EGR input tube in the throttle body. (I needed a dentist's mirror to get in there and see it.) I cleared out the carbon (chunks of it) and...