DR-18C Checking EGR Valve Operation

1. With engine running and EGR valve vacuum line disconnected, connect an auxiliary vacuum supply to the EGR valve.
2. Disconnect idle motor harness connector, then with engine at idle speed, slowly apply vacuum.
3. If engine speed begins to drop when applied vacuum reaches 2 1/2---3 1/2 inches, proceed to step D. DR-18D EGR Valve Vacuum Chamber For Leaks
4. If engine speed does not drop during step 2, replace EGR/back pressure valve assembly.