System Testing
- Check hoses for proper routing and condition. Cold start engine and run at idle. Watch secondary EGR valve and be sure it does not operate as engine speed is increased to 2500 RPM. If it does, replace the thermo valve.
- Warm engine until coolant is at 131°F (55°C). Increase engine speed to 2500 RPM. The secondary EGR valve should now be operating. If not, check EGR control valve and thermo valve and replace as necessary.
- Detach Green striped hose from thermo valve. Connect hand vacuum pump and apply vacuum. If no vacuum is available through thermo valve, valve is good.
- Disconnect Green stripe hose from nipple of carburetor and connect a vacuum pump to Green stripe hose end. While opening sub EGR valve by pulling it by hand, apply 9.8 in Hg vacuum with a vacuum pump.
- If idling speed becomes unstable, the secondary EGR valve is operating properly. If idling speed remains unchanged, valve is not operating properly. Replace EGR valve.