Hi,
I'm french and I don't know what is IAC;wich  total words please ? because
it seems the same problem as mine (1998)
Claude

Replace all plugs and wires with brand new ones before troubleshooting.
When the engine is cold and running disconnect the IAC valve - does this
change the idle or cause the truck to stall?  If yes the IAC is working.  If
No, you could have a bad PCM output or wire harness short/open (you already
changed valve).  Also check that the bypass to the IAC is not plugged.  On
the Explorers with the EEC-V computer aprox. 97 and up, the computer had to
be reset when changing the IAC valve.  Disconnect the battery for 15 minutes
then reconnect,  the computer will retrain it's settings after 15 minutes
worth of  idling.  Also check for any trouble codes,  the EGR valve needs to
be functioning properly before attempting to fix any idle problems.  Another
possibility is an air leak on a vacuum hose, so check for leaks, cracks or
loose fittings.  Good luck.