Intake Air Bypass Control Valve Test

1. Hold the engine at 3,000 rpm with no load (in Park or neutral) until the radiator fan comes on, then let it idle.
2. Disconnect the air assist hose (A) from the IAC valve (B) then connect it to a vacuum pump/gauge (C).
   Fig 1: Connecting Vacuum Pump/Gauge

   Courtesy of AMERICAN HONDA MOTOR CO., INC.
3. Start the engine, then let it idle.
4. Check the vacuum.

   Is there any vacuum 

   1. YES  - Go to step 5.
   2. NO  - Repair the air assist hose.
5. Disconnect the air assist hose from the vacuum pump/gauge, then connect the air assist hose, the IAC valve and the vacuum pump/gauge by using a three-way joint (D).
6. Disconnect the IAC valve 3P connector.
7. Check the vacuum.

Is there vacuum above 40 kPa (300 mmHg, 12 in. Hg)? 

1. YES  - Replace the IAC valve.
2. NO  - The intake air bypass control system is OK.