California Emissions

EGR Mounting:

EGR System Operation

The EGR system routes exhaust gases from the exhaust manifold to the intake manifold during specified engine operating conditions. The EGR valve is opened by ported manifold 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.

EGR Transducer Operation:

VALVE OPERATION
The valve used on this system is a backpressure type that is controlled two ways. First, the computer controls the vacuum through the EGR solenoid, turning the vacuum on or off. Second, a backpressure transducer measures the amount of exhaust back pressure on the exhaust side of the EGR valve and varies the strength of the vacuum signal applied to the EGR valve. The computer will prevent EGR operation at start-up when engine temperature is below 35° F, by turning on the EGR solenoid. When coolant temperature reaches 170° F the EGR solenoid is de-energized and vacuum will be available.