EGR System
- If both EGR valve and thermo vacuum valve are functioning correctly, apply about 8 in. Hg vacuum to EGR valve with hand vacuum pump. With engine warmed up, either rough idling or engine stall should occur.
- If engine idle does not change, check EGR pipe and gas passages for clogging and leaks. Clean or replace if necessary.
NOTE:
On 2WD Federal models, engine must have been running 8 minutes or more before performing this test.