Dual EGR Valve
- Check hoses for proper routing and condition. Cold start engine and run at idle. Place finger under EGR control valve to check for operation of secondary valve while increasing engine speed to 2500 RPM. If valve operates, replace thermo valve.
- Warm engine until coolant temperature exceeds 131°F (55°C). Place finger under EGR control valve and increase engine speed to 2500 RPM. Secondary valve should operate. If valve does not operate, check EGR valve or thermo valve and replace as required.
- Detach Green stripe hose from thermo valve. Connect hand vacuum pump to thermo valve and apply vacuum. If no vacuum is available through valve, thermo valve is okay. Remove vacuum pump and reconnect hose.
- Detach Green stripe hose from carburetor nipple and attach vacuum pump to hose. With engine idling, manually open sub EGR valve by pulling and at same time apply 6 in. Hg vacuum to hose. If idle becomes rough, secondary valve is okay. If idle does not change, EGR valve is improperly operating and must be replaced.