Federal

PURPOSE
Exhaust gas recirculation reduces oxides of nitrogen emissions in the vehicle exhaust. The EGR system uses partial recirculation of exhaust gases from a port in the cylinder head to a port in the intake manifold to lower combustion chamber temperature.

OPERATION
When the thermal vacuum valve determines operating temperatures are suitable for EGR operation it routes ported vacuum to the EGR valve diaphragm. The EGR valve controls the flow of exhaust gas in response to ported vacuum. At partial throttle settings ported vacuum is high and the EGR valve is open. At full throttle and idle port vacuum is low and the EGR valve remains closed.