Exhaust Gas Recirculation: Description and Operation
PURPOSE/OPERATIONThe exhaust gas recirculation 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 and reduce oxides of nitrogen.
When the electronic control module determines conditions are suitable for exhaust gas recirculation operation it disconnects the ground supply to the solenoid. This allows the solenoid to connect the inlet and outlet ports, allowing ported manifold vacuum to be applied to the exhaust gas recirculation valve diaphragm.
The exhaust gas recirculation valve controls the flow of exhaust gas in response to ported vacuum. At partial throttle settings ported vacuum is high and the exhaust gas recirculation valve is open. At full throttle and idle port vacuum is low and the exhaust gas recirculation valve remains closed.
The exhaust gas recirculation system is also equipped with a temperature sensor in the passage for self-diagnostic purposes. It is used to signal the engine control module when the exhaust gas recirculation valve is operating.