EGR Functional Tests

The complete EGR system should be inspected and tested at the time intervals recommended by the manufacturer. To assure proper operation of this system all passages and moving parts must operate properly free of deposits, also hoses and connections must be free from leaks. Ambient temperature in the area of the vehicle must be above 68° F for this test.




Warm up engine and allow the engine to idle, in neutral, with the carburetor throttle closed; then abruptly accelerate the engine to approximately 2000 RPM, but not over 3000 RPM. Visible movement of the EGR valve stem should occur during this operation. This can be determined by change in the relative position of the groove on the EGR valve stem. This operation should be repeated several times to confirm movement. Movement of the stem indicates that the control system is functioning correctly.
If control system is functioning properly, the valve and passages may be checked for exhaust gas flow by applying a vacuum of at least 10 inches Hg directly to the EGR control valve with the engine warm and idling in neutral. Idle speed should drop 150 RPM or more when vacuum is applied. This reduction in idle speed confirms that exhaust gas recirculation is taking place. If the speed change does not occur, or is less than that specified, exhaust deposits in the EGR valve or intake manifold EGR passages are indicated.