Originally Posted by rycodge
Again, if I disconnect the IAC valve, the car runs great and idles just as you'd expect a car to idle at.
That's a good sign that the IAC is bad. I usually recommend people remove the IAC, and clean it before purchasing a replacement. Afterwards, reset the A/F ratio by first warming the engine up by driving around, then disconnect the battery for 10 mins or so. Reconnect the battery, and start the engine. The idle should go up, then settle around 1k rpm. Allow the engine to idle for 5 mins without touching the accelerator. During this time you might notice slight fluctuations in the idle- that's normal. Once the ECU is done with the A/F test, the idle should settle around 700 rpm. That should fix it- if the IAC is not damaged.