System Operational Test

SYSTEM TEST

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

Connecting Vacuum Gauge To Three-way Tee:

NOTE: When disconnecting the vacuum hoses, mark or label them to ensure proper routing when reconnecting.


COLD ENGINE TEST - Coolant temperature is below 20~C (68~F)
1. Disconnect the green striped vacuum hose from the EGR Valve.
2. Using a three-way terminal and vacuum hose, connect a hand vacuum pump into the EGR valve line.
At this point, do not apply vacuum.
3. Quickly depress the accelerator pedal to race the engine.
No change in vacuum (atmospheric pressure) should be detected.

AFTER THE ENGINE IS WARM- Coolant temperature is above 80~C (176~F)
4. Again quickly depress the accelerator pedal to race the engine. Vacuum should rise temporarily to 3.9" or more.

Checking The Operation Of The EGR System:

5. Remove the three-way terminal and connect the vacuum pump directly to the EGR valve.
6. Check to see that the engine stalls or the idle is unstable when a vacuum of 6.8" is applied to the EGR valve.
If there is no change in the engine rpm, it is possible that the passages or the valve may need to be cleaned.