Exhaust Gas Recirculation System (EGR)

Fig. 119 Exhaust Gas Recirculation (EGR) Operation:

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 for any indication of binding or sticking by moving diaphragm of control valve upward with finger.
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, Fig. 119.
4. When engine coolant temperature is above temperature specified in figure, ensure EGR control valve operates when engine speed is raised from idling to 2000-2500 RPM.
5. If EGR control valve does not operate properly in step 4, check as follows:
a. Increase engine speed to 2000-2500 RPM.
b. Ensure that thermal vacuum valve is closed and throttle vacuum is present at EGR control valve side of vacuum hose.
c. If vacuum is weak or nonexistent, replace thermal vacuum valve.
d. If there is vacuum, replace EGR valve.