Exhaust Gas Recirculation: Description and Operation

Fig. 8 EGR valve.:

This system routes a certain portion of exhaust gas from the exhaust manifold to the intake system. This modifies the combustion properties of the air/fuel mixture to reduce exhaust emissions. The flow of exhaust gasses is regulated by restrictors on most models.
The operation of the EGR valve, Fig. 8, is regulated by the position of the throttle switch. There is no EGR operation at idle or at full throttle. This system is also designed to delay EGR function when coolant temperature is below 95°F, and when vehicle speeds exceed 60-65 mph. These functions are controlled by the EGR controller, which is mounted in the trunk of the vehicle.