Thanks Bluegrass for answer but what could I clean or check to maintain correct idle speed? Mine when warm is 1200 in Park and 1300rpm in Drive at stop light. I know this is wrong but Ford Dealer mechanic did not catch this and I spent $77 to be told it is o.k. I know better. I used to mess with restorations and am not scared to clean or check but not sure what to check? Bluegrass or anyone else please advise. 2002 5.4 Auto Lariat SC. Thanks in advance.

 

Well, you being unfamiluar with your engine, I can't tell you much by this medium, that would be more than just words.
Suggest you buy a copy of the Haynes Repir Manuel #36059 on 97-02 trucks. About $15.
Look in chapter 6-2. There you will see a figure 1.1b photo showing 12 locations of different parts.
Part #3 is the IAC and it's mounted on the throttle body.
Hope this will be helpful and a start on solving the problem.
I am trying not to lead you into creating more problems without some reference to use.The high idle , of course, is extra air entering the intake just the same as the old carb engines.
The idle air control is a computer controlled solenoid that adjusts air around the throttle plate instead of haveing to open the plate it'self.
You can assume until proven otherwise that either the IAC is not closing down enough, the throttle plate is hanging open for some reason or maybe someone has adjusted the throttle plate open too far and it can't close, causing the high idle.
As I mentioned before, there is always the possibility of air entering at some other location causing the same action.
Good luck with it. Best I can offer you at the moment until you get a chance to check these areas out.