Emission Control Systems: 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.

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

The VECI decal shows the components of the emission control system with the correct vacuum hose routing. The VECI decal shows the color stripe of the vacuum hoses.

4.6l LH Component Locations:

4.6l RH Component Locations:

RH Component:

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.






The EGR valve to exhaust manifold tube :
^ connects the exhaust manifold to the EGR valve.
^ has two tubes connecting to the differential pressure feedback EGR sensor for EGR flow monitoring.

4.6L Engine Shown, 5.4L Engine Similar:

The differential pressure feedback sensor:
^ monitors the EGR flow rate through the EGR valve tube.
^ sends an EGR flow rate signal to the PCM.

4.6L Engine Shown, 5.4L Engine Similar:

The EGR vacuum regulator solenoid uses input from the PCM to change the EGR valve operation.

The PCV system uses intake manifold vacuum to ventilate the crankcase and return the fumes to the intake manifold for combustion.
The PCV valve also:
^ controls the amount of ventilating air and blow-by gases going to the intake manifold.
^ prevents backfire from reaching the crankcase.