Exhaust Gas Recirculation: Description and Operation

Exhaust Gas Recirculation:

Fig. 42 Integrated electronic EGR valve:

SYSTEM DESCRIPTION

The EGR system routes exhaust gases from the exhaust manifold to the intake manifold at specified engine operating conditions. The EGR valve is opened to let exhaust gas flow into the intake manifold. The exhaust gases then combine 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 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.

VALVE OPERATION

The integrated electronic EGR valve functions similar to a standard EGR (ported vacuum) valve with a remote vacuum regulator, except the regulator and pintle position sensor are sealed in a black plastic cover. The regulator and position sensor are not serviceable. There is a serviceable filter that provides clean fresh air to the regulator, along side the vacuum tube. The ECM provides a variable current to control EGR operation. Inputs form the Coolant sensor, Manifold Air Temperature, and engine rpm all assist in controlling the current to the EGR valve.

EGR VALVE IDENTIFICATION

An electronic EGR valve will have a non-removeable, black, plastic top with a laser marked part number attached.