EGR Valve: Description and Operation

EGR Valve ID:

EGR Flow:

EGR Valve Components:

DESCRIPTION
The EGR valve regulates the amount of exhaust gas fed to the engine. This mixture is dependent upon the height of the pintle above the orifice in the base of the valve. The EGR system is comprised of the following subassemblies:

- Bobbin and Coil (Solenoid) Assembly.
- Armature Assembly.
- Base.

CONSTRUCTION
The bobbin and coil (solenoid) assembly consists of one solenoid that is encapsulated to maximize reliability, seal coils from the environment, and prevent movement of the coils and terminal. Inside the solenoid (bobbin and coil) assembly is an armature assembly, consisting of a pintle and valve assembly, two seals, retaining washers, a seal spring, an armature spring, and a bearing. The valve pintle shaft is sealed from the exhaust chamber by a bearing. In addition, an armature shield, held in place by a compression spring, deflects exhaust gas from the shaft and the armature. The base adapter and base plate make up the base assembly.

As mentioned above the PCM controlled EGR valve regulates the amount of exhaust gas fed to the engine. This device offers more precise EGR flow metering than a back pressure or digital type valve and superior emission control and driveability. The PCM monitors the following sensors to control the linear EGR valve:

- Engine Coolant Temperature (ECT) sensor.
- Throttle Position (TP) sensor.
- Manifold Absolute Pressure (MAP).
- Intake Air Temperature (lAT).
- Throttle Switch (ISC).
- RPM data.
- Vehicle Speed Sensor (VSS).

OPERATION
Output messages are then sent to the EGR system indicating the proper amount of exhaust gas recirculation necessary to lower combustion temperatures. The solenoid assembly is energized by 12 volt current which enters the valve through an electrical connector, then flows through the solenoid assembly to the POM and creates an electromagnetic field. This field causes the armature assembly to be pulled upward, lifting the pintle a variable amount off the base. The exhaust gas then flows from the exhaust manifold (through the orifice) to the cylinder distribution channels. The height of the pintle is read by the pintle position sensor, and the PCM closes the loop on desired position versus actual position read, changing the pulse width modulated command to the solenoid accordingly, until the actual pintle position equals the desired pintle position. This results in improved flow accuracy. The EGR Valve is unique in that the PCM continuously monitors pintle height and continuously corrects it in order to obtain accurate flow in a "Closed Loop" system. When the solenoid is de-energized (PCM opens the circuit), the pintle is sealed against the orifice, blocking exhaust flow to the cylinder distribution channels.