Exhaust Gas Recirculation System (EGR)

1. Make a thorough visual check of system, wiping away oil as necessary to facilitate inspection. Replace any cracked or broken hoses.
2. With engine off, check EGR control valve on vehicles with gasoline engine for any indication of binding or sticking by moving diaphragm of control valve upward with finger. On other vehicles with diesel engine, use vacuum gauge to check for binding or sticking in both the upward and downward direction.
3. Start engine to check EGR control valve and thermal vacuum valve for normal operation. Place a finger on diaphragm of EGR control valve to check operation.
4. When engine coolant temperature is below 104 degrees F., ensure that EGR control valve does not operate when engine speed is raised from idling to 3000-3500 RPM.
5. When engine coolant temperature is above temperature specified in step 4, ensure EGR control valve operates when engine speed is raised from idling to 2000-2500 RPM.
6. If EGR control valve does not operate properly in step 5, check individual components.