IAC Valve Operation
WARNING: This page is about a different car, the 2002 Lexus RX 300 and 2002 Lexus ES 300. However, it is still accessible from the selected car via links, so may be relevant.
Remove throttle body. Remove IAC valve from throttle body. Check IAC valve position. IAC valve should be in half open position. See Fig 1. Connect IAC valve connector to IAC valve. Turn ignition on and observe IAC valve operation. IAC valve should move to fully closed, fully open and then to half open position within .5 seconds of turning ignition on. If IAC valve operation is not as specified, replace IAC valve and retest.