Air Control Valve: Inspection

WARNING: This page is about a different car, the 2002 Lexus LS 430. However, it is still accessible from the selected car via links, so may be relevant.

Turn air conditioning switch off.
Check idle-up.
1. Start the engine and run it at idle.
2. Fully turn the steering wheel.
3. Check that the engine rotations decrease when the vacuum hose of the air control valve is pinched.
  
  Fig 1: Pinching Air Control Valve Vacuum Hose
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
4. Check that the engine rotations increase when the hose is released.