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Cold Engine

  1. Disconnect and plug lower air suction hose from anti-afterburn valve. Remove air cleaner cover and filter. Start engine and check for bubbling noise at air suction port at idle. If a bubbling noise is not heard, proceed to step 5).
  2. If bubbling noise is heard, check for voltage at air suction control solenoid valve (Yellow/Green wire). If there is voltage, turn ignition on and check for voltage at control unit connector (Blue wire). There should be voltage.
  3. If there is no voltage, check Blue wire between ignition coil and control unit. Check 15 MPH speed sensor, thermosensor, intake air temperature sensor, vacuum switch A and vacuum switch C. Turn ignition on, check for voltage at control unit connector (Black/Yellow wire).
  4. There should be voltage. If there is no voltage, check wiring. Check Brown/Black wire for continuity between control unit and ground. There should be continuity.
  5. If bubbling noise is not heard, disconnect vacuum hose No. 5 from air suction cut-off diaphragm. If there is vacuum, replace air suction control solenoid valve and retest. If there is no vacuum, replace air suction cut-off diaphragm and retest.
  6. Ensure engine coolant is below 95°F (35°C) for Calif. models or 122°F (50°C) for Federal models. Disconnect intake air temperature switch connector. Check for a bubbling noise at idle. If noise is heard, see HOT ENGINE test.
  7. If bubbling noise is not heard, check for voltage at air suction control solenoid valve (Yellow/Green wire). If there is no voltage, turn ignition on and check for voltage at control unit connector (Blue wire). There should be voltage.
  8. If there is no voltage, check Blue wire between ignition coil and control unit. Check 15 MPH speed sensor, thermosensor, intake air temperature sensor, vacuum switch A and vacuum switch C. Turn ignition on, check for voltage at control unit connector (Black/Yellow wire).
  9. There should be voltage. If there is no voltage, check wiring. Check Brown/Black wire for continuity between control unit and ground. There should be continuity. If there is voltage, replace air suction control valve and retest.
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