Engine Emission Control: Notes

WARNING: This page is about a different car, the 2009 Mercury Grand Marquis and 2009 Ford Crown Victoria. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Do not permanently remove or render inoperative any part of the vehicle emission control system including related hardware. Failure to comply may violate applicable state and federal laws.

The engine emission control consists of the:

EGR system.
PCV system.

The EGR system returns a small amount of exhaust gas into the intake manifold. This reduces the overall combustion temperature. Cooler combustion temperatures provide a significant reduction of the oxides of nitrogen (NOx) in the exhaust emissions.

The EGR system module tube:

connects the exhaust manifold to the EGR system module and provides a path to deliver exhaust vapors to the EGR system module.

The EGR vacuum regulator solenoid uses input from the PCM to achieve the calibrated level of EGR flow for various engine operating conditions.

The PCM controls the EGR system module opening via the vacuum regulator solenoid. When the EGR system module opens, exhaust gas flows to the intake manifold. The EGR system module transducer measures the delta pressure across the orifice located in the EGR system module gasket. This delta pressure signal is sent to the PCM providing an indication of the EGR mass flow that was delivered.

The amount of recirculated exhaust gas depends on:

engine RPM.
intake manifold vacuum.
exhaust backpressure.
engine coolant temperature.
throttle position.

The PCV system uses intake manifold vacuum to ventilate blow-by vapors from the crankcase and return the vapors to the intake manifold for combustion. The PCV valve varies the amount of blow-by gases returned to the intake manifold based on available engine vacuum. The PCV valve also prevents the entry of combustion backfiring into the crankcase.