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 CONTROL/VENT SOLENOID VALVE FUNCTION
EGR Control/Vent Solenoid Valve Function:
1. Disconnect the vacuum hoses, and electrical connection to the control solenoid valve. Blow through port A of the solenoid valve and verify that air does not flow. If air flows through the valve, the valve is defective and must be replaced.
2. Apply 12 volts, and ground to the valve as shown. Then blow through port A of the solenoid valve. Air should flow through the valve. If air does not flow, the valve is defective and must be replaced.
EGR Control/Vent Solenoid Valve Function:
3. Disconnect the vacuum hose from the vent solenoid portion of the control/vent solenoid valve assembly. Blow through port B of the valve and verify that air flows. If air will not flow at this point the valve is defective and must be replaced.
4. Apply 12 volts and ground to the terminals as shown and then blow through port B of the vent solenoid. Air should not flow with the solenoid engaged. If air does flow the valve is defective and must be replaced.
EGR VALVE FUNCTION
EGR Valve Function Test:
1. Manually actuate the EGR valve diaphragm with a finger, make sure the valve moves freely, and make sure spring tension is present. If the valve will not move, and/or there is no spring tension, it is defective and must be replaced.
EGR Valve Function Test:
2. Connect a vacuum tester to the EGR valve. START and warm up the engine to operating temperature.
3. With the engine at idle apply 40-60 mm-Hg (1.6-2.4 in-Hg) of vacuum. The engine should idle rough at this level, and stall with additional vacuum. If no roughness is present, there is no drop in engine rpm, and the engine will not stall with additional vacuum, the valve is not functioning. Check for obstruction to the EGR valve, and if no obstruction is present refer to Powertrain Management/Emission Control Systems/Exhaust Gas Recirculation/Service and Repair. If after cleaning, the EGR valve does not function, it must be replaced.
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.
EGR VACUUM RESERVOIR FUNCTION
Vacuum Reservoir Function Test:
1. Remove the vacuum reservoir, and attach a vacuum pump as shown. Apply a vacuum to port A of the reservoir and verify that no vacuum is held. If vacuum is held at port A the reservoir is plugged and must be replaced.
Vacuum Reservoir Function Test:
2. Switch the vacuum pump to port B of the reservoir and apply a vacuum. Verify that the reservoir will hold vacuum at this point. If the reservoir will not hold vacuum it is defective and must be replaced.