Exhaust Gas RECIRCULATION (EGR)

To lower oxides of nitrogen (NOx) exhaust gas emissions, an Exhaust Gas Recirculation (EGR) system is used. The EGR system introduces exhaust gases into intake system. The exhaust gases are noncombustible gases which, when combined with the incoming air/fuel mixture, lower peak combustion chamber temperatures.

EGR valve receives ported operating vacuum from a control unit regulated EGR vacuum solenoid. Vacuum signal to EGR valve is further controlled by a vacuum modulator located in the vacuum line between the EGR solenoid and ported vacuum supply, and a Coolant Temperature Override (CTO) vacuum switching valve. When coolant temperature is less than 127-149°F (53-65°C), vacuum will not pass through CTO vacuum switching valve. This prevents EGR action during cold engine operation when NOx emissions are not produced and EGR is not desirable.