Exhaust Gas Recirculation: Testing and Inspection

EGR Diagnosis:

TEST DESCRIPTION: Numbers refer to circled numbers on the diagnostic chart.

1. This test checks that the EGR valve is mechanically functional.
2. This test checks that the vacuum is available to operate the EGR valve.

FUNCTIONAL TEST

Connect a hand-held vacuum pump to the vacuum nipple at the top of the EGR valve and apply 24 kPa vacuum. The diaphragm (visible at the bottom of the EGR valve) should move fully up and hold position at that vacuum, without leaking down.

If EGR passages in the inlet manifold indicate excessive build-up of deposits, the passages in the valve itself may be clogged.

Thermal Vacuum Valve:

Vacuum Gauge Connection:

1. Disconnect 3-way vacuum hose connector to charcoal canister, between EGR and TVV.
2. Connect a vacuum gauge to the vacuum tee between EGR and TVV.
3. When the engine is cold, start the engine and check that the vacuum gauge indicates 0 kPa at any engine speed.
4. With the engine at operating temperature check that the vacuum gauge indicates 0 kPa at idle and over 6.7 kPa at 3500 rpm. Hold the engine rpm at 3500 rpm, disconnect and plug the vacuum hose to the EGR valve. Check that the engine speed increases a little.
5. Stop the engine and push the diaphragm by hand and release it. Check that the diaphragm plate returns smoothly to original position.
6. If a problem is found inspect each part.
7. Reconnect all hoses to original connections.

Replace the EGR valve if:

^ Cracks in the diaphragm prevent the EGR from holding.
^ Deformation of the valve seat or carbon deposits will cause the valve to stick open.