Well
The IAC valve is the
Idle Air Control Valve.
It is the same unit found on most ford V-6's 86 +
You can clean it with carb cleaner, it's easy.
Take it off the intake manifold with the two 8mm bolts.
remove the wire clip
unscrew (2 phillips) the electronic sensor from the mechanical valve body
take the mechanical vavle body and spray the hell out of it with carb cleaner.
Turn the valve around and around so you can get at all sides of the piston
Use Q tips to get the hard to reach stuff.
Make sure you open and close the vavle several times while cleaning and drying.
let it dry completely.
Re-install, you can even cut a new gasket for it if you ruined the old one.
Thats all the service these baby's require. there is no reason to buy a new one, it's a simple little spring actuated valve.
I clean mine probably once a year, along with the mass air sensor and throttle body, but then I'm a fanatic.
Cleaning the MAS and IAC will really smooth out any rough idle that your 4.0L may develop.
Oh yeah be sure to reset the computer by disconnecting the - battery terminal for 30 seconds. Any time you change the reading a sensor will be feeding the computer (A dirty MAS sends a different signal then a clean one) you should re-set the CPU.
Good luck!
