The rotor in the IAC can sieze and cause a wide range of issues. If it siezes in a open position, it will act like a vacuum leak. If it siezes in a closed position, the engine will want to die at idle and will require the TB butterfly be slightly open to run.

The rotor can sieze-up rather easily, especially when you have a aftermarket intake and/or disable the TB heater, due to condensation forming in the IAC's internal passageway.

So take a Dremel and cut slots in the 5pointed tamperproof screws retaining the IAC to the bottom of the TB and remove them with a straightslot screwdriver. Now take that same Dremel and slot the screws retaining the electrical portion to the rotor and passageway and seperate the two parts like this,


You can see the carbon and dirt deposits in the passageway in this pic.


Now clean the passageway with a brake cleaner and toothbrush. Drain all the cleaner and put the IAC passageway submerged in penetrating oil for a few hours.

Now take a drill and some spare vacuum/fuel tubing, a piece of a bic pen and spin that rotor. Try to leave some oil in the passageway for lubrication, but watch out the oil will be thrown around everywheres if you are not carefull.




IF AT THIS POINT the rotor does not spin fairly freely, the IAC will need to be replaced. Eventually the rotor will sieze again, but adding a little light oil into the IAC port in the bottom of the TB at your oil change time and before storage will stave this off for awhile.