Hot Engine
- Run engine to operating temperature. Check operation of thermo valve C. Attach vacuum gauge to vacuum hose No. 27 at tubing manifold. Vacuum should not be present at idle. If there is no vacuum, check air suction valve. If vacuum is present, replace thermo valve C and retest.
- When checking air suction valve, remove air cleaner cover and filter. Start engine and run at idle speed. Check for bubbling noise from air suction port. See Fig 1
. If bubbling noise is heard, proceed to step 3).
Courtesy of AMERICAN HONDA MOTOR CO., INC.
- If bubbling noise is not heard, disconnect hose No. 5 from air suction cut-off diaphragm and check for vacuum. If vacuum is present, replace air suction cut-off diaphragm and retest. If there is no vacuum, reconnect vacuum hose No. 5.
- Disconnect hose No. 32 from control box at vacuum hose manifold. Check for vacuum at vacuum hose manifold. If there is no vacuum, check vacuum hose No. 32 for blockage or leakage. If no blockage or leakage is found, replace air bleed valve B and retest.
- If vacuum is present, check for voltage at air suction control valve in box No. 1 (Blue/Green wire on man. trans. and Green/Red wire on auto. trans.). If voltage is not present, check intake air temperature sensor and vacuum switch C.
- Turn ignition on and check for voltage at control unit Black/Yellow wire. If there is no voltage, check wiring. Check Brown/Black wire for continuity between control unit and ground. Continuity should be present.
- If voltage is present, replace air suction control valve and retest. Raise engine speed above 3500 RPM. If bubbling noise is not heard, system is okay. If bubbling noise is heard, check for voltage at air suction control solenoid valve (Green/Red wire on auto. trans. and Blue/Green wire on man. trans.) in box No. 1.
- If voltage is present, check intake air temperature sensor and vacuum switch C. Turn ignition on and check for voltage at control unit Black/Yellow wire. Voltage should be present. If there is no voltage, check wiring. Check Brown/Black wire for continuity between control unit and ground. Continuity should be present.
- If there is no voltage, replace air suction control solenoid valve and retest. Heat air bleed valve to 140°F (60°C). Ensure bubbling noise stops. If noise does not stop, replace air bleed valve B.