Exhaust Gas RECIRCULATION: Description
WARNING: This page is about a different car, the 2005 Jeep Liberty. However, it is still accessible from the selected car via links, so may be relevant.
The task of the Exhaust Gas Recirculation (EGR) is to regulate the fresh air supply to the engine by means of the exhaust gas recirculation system, in favor of clean combustion. The EGR system reduces oxides of nitrogen (NOx) in the engine exhaust. This is accomplished by allowing a predetermined amount of hot exhaust gas to recirculate and dilute the incoming charge air.
A malfunctioning EGR system can cause engine stumble, sags, or hesitation, rough idle, engine stalling and poor driveability.