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 diesel engine, use vacuum gauge to check for binding or sticking in both upward and downward direction.
3. Start engine to check EGR control valve and thermal vacuum valve for normal operation. Place mirror under diaphragm of EGR control valve.
4. When engine coolant temperature is below 77-86°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 as follows:
a. Ensure that thermal vacuum valve is open and that sub-venturi vacuum is present at vacuum amplifier side of vacuum hose, using vacuum gauge.
b. If vacuum is nonexistent on replace thermal vacuum valve.
c. If there is vacuum replace vacuum amplifier.