Functional Check EGR System

On models with electronically controlled EGR, refer to EGR system checks in ``Computer Command Control (C-3) System,'' ``Electronic Fuel Injection'' or ``Diesel Electronic Control (DEC) System'' sections.
1. Place finger under EGR valve and lift up on diaphragm plate. Plate should move up and down freely without binding or sticking. If not, replace valve. If valve is hot, it may be necessary to wear gloves to avoid injury.
2. Connect vacuum gauge to EGR valve vacuum signal line using a T-fitting. Start engine and run at part throttle.
3. Vacuum gauge should indicate at least 5 inches Hg at part throttle once engine reaches normal operating temperature. If not, check control valves, hoses and vacuum source, and repair as needed.
4. With engine running as in step 3, disconnect vacuum hose to EGR valve. Diaphragm plate should move and engine speed should increase.
5. Reconnect vacuum hose to EGR valve. Diaphragm plate should move and engine speed should decrease.
6. If diaphragm moves but there is no change in engine speed, check manifold passages for blockage. If passages are clear, EGR valve is defective.
7. If diaphragm does not move in steps 4 or 5 and vacuum signal is within specifications, EGR valve is defective.