Engine Emission Control

WARNING: This page is about a different car, the 2005 Mercury Mountaineer and 2005 Ford Explorer. However, it is still accessible from the selected car via links, so may be relevant.

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 system consists of the:

positive crankcase ventilation (PCV) system.
exhaust gas recirculation (EGR) system.

Fig 1: Identifying Typical Vehicle Emission Control Information (VECI) Decal

Courtesy of FORD MOTOR CO.

The Vehicle Emission Control Information (VECI) decal shows:

components of the emission control system.
the correct vacuum hose routing.
the color stripe of the vacuum hoses.

For additional information, refer to IDENTIFICATION CODES .

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

Fig 2: Identifying EGR System Components Diagram

Courtesy of FORD MOTOR CO.

The EGR system returns a portion of the exhaust gas to the intake manifold to reduce the combustion temperature. This results in lower nitrous oxide formation.

The PCM controls the EGR system module. When the EGR system module valve opens, exhaust gas flows to the intake manifold.

The EGR system module to exhaust manifold tube:

connects the exhaust manifold to the EGR valve.

The EGR system module transducer:

monitors the EGR system module flow rate through the EGR to exhaust manifold tube.
sends an EGR system module flow rate signal to the PCM.

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

The PCV valve:

controls the amount of ventilating air and blow-by gases going to the intake manifold.
prevents a backfire from reaching the crankcase.