System Test

Fig. 54 Anti-Afterburn Valve:

COLD ENGINE
1. Test for vacuum signal from the anti-afterburn valve.
a. Disconnect the lower air suction hose at the anti-afterburn valve, Fig. 54.
b. Start the engine and check for vacuum at idle. There should be no vacuum.
c. If there is vacuum, replace the anti-afterburn valve and re-test.

Fig. 55 Checking Vacuum To The Anti-Afterburn Valve:

2. Test for vacuum to the anti-afterburn valve.
a. Remove the #31 hose, Fig. 55, and install a cap on the anti-afterburn valve.
b. Connect a vacuum gauge to hose #31 and start the engine. Vacuum should be available at idle.
c. If there is no vacuum, go to "ANTI-AFTERBURN CONTROL SOLENOID VALVE" test.


3. Test valve operation.
a. Block the rear wheels and set the parking brake.
b. Jack up the front of the car and set on jack stands.
c. Disconnect the lower air suction hose from the anti-afterburn valve, Fig. 54.
d. Place the shift lever in second gear (set shift selector to 2 on cars with automatic trans.) and accelerate then suddenly release the throttle and check for vacuum during deceleration above 15 mph.
e. While the engine is decelerating, vacuum should be available from the port on the valve.
f. If vacuum is available, go to HOT ENGINE test.
4. If vacuum is not available in step 3, test for vacuum input operation.
a. Disconnect #31 vacuum hose at the anti-afterburn valve and connect a vacuum gauge to the hose, Fig. 55.
b. Start the engine and, with the car in gear, check for vacuum above 15 mph.
c. If there is no vacuum, replace the anti-afterburn valve and re-test.
d. If there is vacuum, go to "ANTI-AFTERBURN CONTROL SOLENOID VALVE" test.

HOT ENGINE
1. With the engine at normal operating temperature, check for vacuum at speed.
a. Disconnect the lower air suction hose at the anti-afterburn valve, Fig. 54.
b. Start the engine and quickly raise the engine speed to 3500 rpm and close the throttle quickly. Vacuum should be available.
c. If there is no vacuum, replace the valve and re-test.
2. Check for vacuum at idle.
a. Disconnect the lower air suction hose at the anti-afterburn valve, Fig. 54.
b. With the engine running at idle, no vacuum should be available.
c. If vacuum is available, replace the anti-afterburn valve and re-test.