Exhaust Gas Recirculation: Testing and Inspection

EGR System Testing:

SOLENOID TEST
Bring the engine to normal operating temperature. Operate at idle speed. Test the EGR solenoid as follows:
^ Check vacuum at solenoid vacuum source hose. Disconnect the line and attach a vacuum gauge to it.
^ Vacuum should be a minimum of 15 inches.
^ If vacuum is low, check the lines for kinks, twists, or a loose connection at manifold fitting.
^ If vacuum is OK, remove gauge, reconnect the line and proceed to next step.
^ Check vacuum at solenoid output port.
^ Disconnect the line and attach a vacuum gauge to output port. Vacuum reading should be zero (no vacuum) at this side of solenoid.
^ If vacuum reading is zero, leave the gauge connected and proceed to next step. If vacuum is present, check solenoid/ECU operation and repair as necessary.
^ Disconnect electrical connector at solenoid and note vacuum at solenoid output port. Vacuum should now be present at output port.
^ If vacuum is present, proceed to EGR valve test. If vacuum is not present, replace the solenoid.

EGR Valve:

EGR VALVE TEST

^ With engine idling at normal operating temperature, accelerate engine to 1500 RPM and release throttle. A definite movement should be noticed in the EGR diaphragm.
^ If diaphragm does not move, check for leaking vacuum lines, faulty vacuum signal to EGR valve or defective EGR valve.
^ With engine idling at normal operating temperature, manually depress EGR valve diaphragm. Engine speed should drop immediately, indicating proper operation of the EGR valve during engine idling.
^ If there is no change in engine speed and the engine is idling properly, exhaust gases are not reaching the combustion chamber, and the probable cause is a plugged passage between the EGR valve and the intake manifold.
^ If the engine idles poorly and the speed is not greatly affected when the EGR valve diaphragm is closed, the EGR valve is not stopping the flow of exhaust gases to the combustion chambers. Check for defective hoses, incorrectly routed hoses or defective EGR valve.