DR-24C Checking EGR Valve Operation

This test must be performed with engine warm.

1. With vacuum line disconnected from EGR valve and engine running, connect an auxiliary vacuum supply to EGR valve.
2. Disconnect idle motor harness connector, then with engine running at idle, slowly apply vacuum.
NOTE: The automatic idle speed motor will attempt to compensate for drop in engine speed from EGR, so idle speed drop may only be momentary at lower applied vacuum level.
3. If engine speed drops when vacuum reaches 2---3.5 inches, proceed to Test 24 step D.
4. If engine speed does not drop, replace EGR/back pressure valve assembly. Check supply tube from manifold for restriction when valve is removed, and clean if required.