Exhaust Gas Recirculation: Description and Operation

SYSTEM DESCRIPTION
The Exhaust Gas Recirculation (EGR) system routes exhaust gases from the exhaust manifold to the intake manifold at specified engine operating conditions. The EGR valve is opened to let exhaust gas flow into the intake manifold. The exhaust gas then moves with the air/fuel mixture into the combustion chamber. Since there is less air/fuel mixture to burn in the combustion chamber during EGR operation, the temperature is reduced enough to limit NOx formation. If too much exhaust gas enters combustion will not occur. Because of this very, little exhaust gas is allowed to pass through the valve, especially at idle. the valve should only open when the engine is at operating temperature and above idle speed. The EGR vacuum control solenoid controls the amount of exhaust gas recirculation.

VALVE OPERATION
The integrated electronic EGR valve functions like a port valve with a remote vacuum regulator, except the regulator and pintle position sensor are sealed in a black plastic cover. The regulator and position sensor are not serviceable. There is a serviceable filter, that provides clean fresh air to the regulator along side the vacuum tube.

EGR CONTROL
This valve has a vacuum regulator, to which the Electronic Control Module (ECM) provides variable current. This variable current provides the desired EGR flow using inputs from the Mass Air Flow sensor (MAF), coolant temperature sensor, and engine rpm.