Emission Control Systems: Description and Operation: Description and Operation

CAUTION: Do not remove any part of the engine emission control system. Operating the engine without the engine emission control system will reduce fuel economy and engine ventilation. This will weaken engine performance and shorten engine life.

All engines are equipped with an Exhaust Gas Recirculation (EGR) system. The function of the EGR system is to reduce the emission of Nitrogen Oxide (NOx).

The engine emission control system consists of the following components:
^ Positive Crankcase Ventilation (PCV) system
^ Exhaust Gas Recirculation (EGR) system

The PCV system uses intake manifold vacuum to ventilate the crankcase and return the fumes to the intake manifold for combustion.

The EGR system returns a portion of the exhaust gas to the intake manifold to reduce the combustion temperature. This reduces the oxides of nitrogen (NOx) in the exhaust emissions.

The PCM controls the EGR vacuum regulator solenoid. The EGR vacuum regulator solenoid controls the vacuum to the EGR valve. When the EGR valve opens, exhaust gas flows to the intake manifold. The differential pressure feedback EGR sensor measures the flow through the EGR valve to exhaust manifold tube and sends a signal to the PCM. A metering orifice in the EGR valve to exhaust manifold tube restricts the flow rate when the EGR valve is open.

All engines are equipped with a Positive Crankcase Ventilation (PCV) system. The function of the PCV system is to circulate blow-by gases from the engine crankcase to the engine intake.

The PCV system consists of:
^ PCV valve
^ PCV tube

For further description and operation, refer to Computers and Control Systems.