Exhaust Gas Recirculation: Testing and Inspection

The EGR valve on the intake manifold must be removed, cleaned and inspected at the mileage intervals as specified. The exhaust gas passages in the intake manifold also should be inspected and cleaned as required.

After cleaning, open the EGR valve manually by pressing down on the pintle, then release.

NOTE: If the valve does not return to the fully closed position, it must be replaced.

Inspect the exhaust gas inlet and discharge passages of the intake manifold for any restriction caused by carbon or lead deposits.

On some six cylinder engines, lead or carbon deposits build up rapidly in the exhaust gas discharge passage upper hole. If the deposits cannot be removed a 9/16 inch drill bit may be used.

With engine idling at normal operating temperature, accelerate engine to 1,500 rpm and release throttle. A definite movement should be noticed in the EGR diaphragm. If diaphragm does not move, check or leaking vacuum lines, faulty vacuum signal to EGR valve, defective EGR valve or back pressure sensor.

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.