Intake Air Bypass (IAB) Control System: Testing

1. Check the IAB control valve shaft for binding or sticking.
2. Check the IAB control valve for smooth movement.
3. Check that (A) of the IAB control valve is in close contact with the stopper when the vacuum hose is disconnected from the IAB control diaphragm. See Fig 4 .
4. Check that (B) of the IAB control valve is in close contact with the full-close screw when you apply 15 in. Hg (380 mm Hg) of vacuum to the IAB control diaphragm. See Fig 5 .
5. If any fault is found, clean the linkage and shafts with carburetor cleaner.
6. If the problem still exists after cleaning, disassemble the intake manifold and check the IAB valve body assembly. See 3.0L V6 -- NSX & NSX-T article.

Fig 1: Identifying Intake Air Bypass (IAB) System Operation

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Fig 2: IAB Control System Diagnostic Flow Chart (1 Of 2)

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Fig 3: IAB Control System Diagnostic Flow Chart (2 Of 2)

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Fig 4: Identifying IAB Control Valve Open Position (No Vacuum)

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Fig 5: Identifying IAB Control Valve Closed Position (Vacuum Applied)

Courtesy of AMERICAN HONDA MOTOR CO., INC.