The IAC is not alwasy the problem ..
can be -->
cheap things -->
dirty air filter ,blocked fuel filter,dirty injectors,spark plugs and leads,throttle body dirty.
expensive things -->
coil pack/dfi heats up and is causing a miss at low revs , fuelpump on its way out , fuel pressure reg stuffed, inlet manifold gasket stuffed , alternator is weak and cant power car on low revs.
try this .. change all your spark plugs and leads , buy can carbie cleaner and spray 1/4 can into throttle body and open up throttle and spray in there and look in there and you will see the IAC air inlet so spray in there as well then let sit for few minutes then get can wd40 and then spray that in there while opening and closing the throttle as this will lubricate the moving parts , change fuel filter and put bottle nulon injector cleaner and fill up with 1/2 tank of premium and go for a drive on a long road or freeway.
If you still have problem then possibly coolant temp sensor is playing up... and the oxygen sensor can also cause idle issues but usually engine light comes on and fuel consumption increase greatly.
One thing to try is when cars first started in the morning , gently touch accelerator and listen to the low revs and if you hear a miss then its definately spark plugs,leads,coilpack dfi as this is what happened to me trying to sort out the miss even when engine was cold it had the miss and coil pack died year later so replaced with new vp one.
I have spent thousands on my vn only because it's 1 owner and got less than 220,000 it. replaced 90% everything ... only things original are the engine,transmission,diff and the computer.
