System Operational Test

The following procedures will allow a basic operational test of the EGR system. Since the EGR operation is controlled by the ECU, refer to COMPUTERS AND CONTROL SYSTEMS for further information concerning testing of the systems operation.

EGR Vacuum Delivery Test:

1. Disconnect the green striped vacuum hose from the EGR valve and connect a hand vacuum pump through a vacuum "Tee".
2. While the engine is cold (coolant temperature less than 68° F (20° C)) race the engine and verify that vacuum is not present.
3. Allow the engine to warm up (coolant temperature greater than 158° F (70° C)).
4. Race the engine and verify that vacuum increases to 3.9 in. Hg (100 mm Hg) or more.

EGR Valve Inspection:

5. Disconnect the vacuum "Tee" and connect the vacuum pump directly to the EGR valve.
6. Using the vacuum pump apply 8.5 in. Hg (215 mm Hg) of vacuum while the engine is at idle and verify that idle becomes unstable.