EGR Functional Tests

1. Start engine and operate at idle speed.
2. With coolant temperature below 131°F, increase engine speed to 2500 RPM and check to ensure that secondary EGR valve is not operating. If secondary EGR valve is operating, replace thermo valve.
3. Allow coolant temperature to exceed 133°F, then increase engine speed to 2500 RPM and check secondary EGR valve operation. If secondary EGR valve does not operate, check EGR control valve and thermal valve and replace as necessary.
4. Disconnect green stripe hose at carburetor and connect a vacuum pump to vacuum hose.
5. While operating sub-EGR valve by hand, apply 5.9 inches Hg of vacuum with vacuum pump.
6. If idle speed becomes unstable, the secondary EGR valve is operating properly. If idle speed remains unchanged, replace EGR valve.