IACV Unplugged = Closed (Set Base Idle)

If you want to test the IAC valve to make sure it will fully close down, you can temporarily unplug it. When you unplug the IAC valve the idle should drop to the base idle. When the car is fully warmed up, and is on base idle, all the air is being controlled on the idle bypass screw. If the idle air bypass screw does not seem to have total control over the idle, the IAC valve may not be shutting down completely, or there is another source of unmetered air.