Exhaust Gas Recirculation (EGR) System: Overview
WARNING: This page is about a different car, the 2011 Mercury Milan, 2011 Lincoln MKZ, 2011 Ford Fusion, 2010 Mercury Milan, and 2010 Ford Fusion. However, it is still accessible from the selected car via links, so may be relevant.
The EGR system controls oxides of nitrogen (NOx ) emissions. Small amounts of exhaust gases are recirculated back into the combustion chamber to mix with the air/fuel charge. As a result the combustion chamber temperature is reduced, lowering NOx emissions.