Air Control Valve: Inspection

Turn air conditioning switch off .
Check idle-up :
1. Start engine and run it at idle.
2. Fully turn the steering wheel.
3. Check that the engine speeds decreases when the vacuum hose of the air control valve is pinched.
  
  Fig 1: Locating & Pinching Vacuum Hose
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4. Check that the engine speeds increases when the hose is released.