Exhaust Gas RECIRCULATION (EGR) Valve

1. Connect a tachometer to engine. Connect vacuum gauge between EGR valve and EGR vacuum port. With engine cold, start engine and check that vacuum gauge indicates no vacuum at idle. Warm engine to operating temperature.
2. Check that vacuum gauge indicates no vacuum at idle. Increase engine speed to 2000 RPM. Vacuum gauge should indicate more than 6 in. Hg. Disconnect and plug vacuum hose to EGR valve. Engine speed should increase. Stop engine, push diaphragm plate by hand and release it. Check that diaphragm plate returns smoothly to original position.
3. If 6 in. Hg was not obtained in step 2), check vacuum hoses and ports for restrictions or leaks. If EGR valve did not perform as stated in step 2), replace EGR valve.

Fig 1: EGR Diagnostic Flow Chart

Courtesy of GENERAL MOTORS CORP.