Federal and Canada

Purpose
Exhaust gas recirculation is used to reduce oxides of nitrogen emissions in the vehicle exhaust.
- 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 engine coolant temperature is above 185° - 205° F (85° - 95° C) the thermo valve closes off the vent port.
- This in turn allows ported manifold vacuum to be applied 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.