Port EGR Valve

EGR System:

PURPOSE
The Exhaust Gas Recirculation (EGR) system is designed to lower NOx (oxides of nitrogen) emission levels created by high combustion temperatures.

OPERATION
The EGR system routes exhaust gases from the exhaust manifold to the intake manifold at specified engine operating conditions. The EGR valve is opened by vacuum 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 varies vacuum which controls the amount of exhaust gas recirculation.

EGR Valve:

CONSTRUCTION
The port EGR valve is controlled by a flexible diaphragm which is spring loaded to hold the valve closed. Vacuum applied to the top side of the diaphragm overcomes the spring pressure and opens the valve in the exhaust gas port. This allows the exhaust gas to be pulled into the intake manifold and enter the engine cylinders.

EGR Valve Identification:

IDENTIFICATION
The ported EGR valve is identified by having NO identification number or letter stamped after the part number.