Exhaust Gas Recirculation: Testing and Inspection

NOTE: If a vacuum line or orifice blockage is suspected as the obvious cause of the malfunction, correct the cause before proceeding.

EGR BACK PRESSURE VARIABLE TRANSDUCER FUNCTION

Back Pressure Variable Transducer:

1. Remove the transducer and connect a vacuum pump to the NO. 3 port on the transducer. Block the NO. 1 port on the transducer.
2. Blow into the exhaust gas port on the transducer, while applying vacuum with the pump. Verify that vacuum is held. If no vacuum is held the transducer is defective and must be replaced.
3. Release the exhaust gas port, and verify that vacuum is not held. If vacuum continues to hold the transducer is defective and must be replaced.

EGR VACUUM REGULATOR SOLENOID FUNCTION

Vacuum Regulator Solenoid:

1. Disconnect the vacuum hoses, and electrical connections from the vacuum regulator solenoid.
2. Blow through the vacuum line at port A and verify that air blows through and flows out of port B. If no air flow is present the solenoid is plugged and must be replaced.

Vacuum Regulator Solenoid:

3. Apply 12 volts and ground to the solenoid connections as shown, and blow through the vacuum line at port A again. Air should flow out through the air filter at this point, and no air should flow out of port B. If this is not the case, the valve is defective and must be replaced.

EGR VALVE FUNCTION

EGR Control Valve Test:

1. Manually actuate the EGR valve diaphragm with a finger, make sure the valve operates freely, and that spring tension is present. If the valve will not move and/or there is no spring tension, the valve is defective and must be replaced.

EGR Valve Test:

2. Connect a vacuum pump to the EGR valve. START and warm the engine to operating temperature. With the engine at idle, apply 40-60 mm-Hg (1.6-2.4 in-Hg) of vacuum to the EGR valve. The engine should idle rough at this level, and stall when more vacuum is applied. If the engine does not idle rough, and will not stall when the vacuum is increased, the valve is not functioning. Check for an obstruction to the valve and if no obstruction is found, refer to Powertrain Management/Emission Control Systems/Exhaust Gas Recirculation/Service and Repair. If after cleaning the system will not function, replace the EGR valve.

DIAGNOSTIC AID: If a functional test of the EGR system is required as part of the emissions testing procedure, the EGR system can be checked by placing a "T" fitting in the vacuum line at the EGR valve, connecting a vacuum gauge to the fitting with a long hose, so that the gauge is visible while driving. Drive the vehicle at approximately 30 mph for a short distance. The EGR system should actuate the vacuum signal to the valve when the engine control system goes into closed loop operation. If the system does not actuate refer to COMPUTERIZED ENGINE CONTROLS/DIAGNOSIS AND TESTING for further test procedures.