Cold Engine
NOTE:
Engine coolant temperature must be below 158°F (70°C).
- Disconnect air suction lower hose from anti-afterburn valve. Start engine and quickly raise engine speed to 2500 RPM and close throttle suddenly. Check for vacuum at air suction lower hose. If there is no vacuum, proceed to step 5).
- If there is vacuum, check for voltage at anti-afterburn control solenoid valve (Green/White wire). If there is no voltage, check for continuity between speed sensor wire terminals and thermosensor wire sensor wire terminals.
- If no continuity, replace thermosensor and retest. If still no continuity, replace speedometer/speed sensor. If there is voltage, disconnect upper vacuum hose at anti-afterburn valve.
- Check for vacuum. If no vacuum, check for leaks or disconnected hose. If hose is okay, replace anti-afterburn control solenoid valve and retest. If there is vacuum, replace anti-afterburn valve and retest.
- Raise front of vehicle and support with jack stands. Set parking brake and block rear wheels. Place shifter in 2nd or "2" position and accelerate. Quickly release throttle and check for vacuum during deceleration at speeds more than 15 MPH. There should be vacuum.
- If there is vacuum, proceed to HOT ENGINE test. If no vacuum, check for voltage at anti-afterburn control solenoid valve at speeds more than 15 MPH. If there is voltage, replace speed sensor. If there is no voltage, disconnect upper vacuum hose at anti-afterburn valve and check for vacuum at speeds more than 15 MPH.
- If there is vacuum, replace anti-afterburn control valve and retest. If no vacuum, disconnect vacuum hose No. 20 from anti-afterburn valve and check for vacuum. If no vacuum, check for leaks or disconnected hose and retest. If there is vacuum, replace anti-afterburn valve and retest.