The Chevrolet EGR valve and motor is the mechanism that recycles your exhaust gases in order to help reduce the amount of nitrogen oxide your engine produces when it is running. This is one of the many smog reduction devices mandated by the US government. It was one of the first of many smog devices and has been on engines since 1973. The activator of the EGR valve and motor is partially done by vacuum on your Chevrolet. For this reason your engine should not have a vacuum leak or this smog device might not function correctly. It is typically located on or near the intake manifold of your engine. The way the Chevrolet EGR valve and motor works in contributing to the reduction of nitrogen oxide from your engine is to reduce the temperature in the combustion chamber. Theoretically this will improve the performance of your engine and help to increase its fuel mileage while reducing the amount of nitrogen oxides it produces. The EGR valve and motor wear out over time because the vacuum valve portion of this part is activated by a polymer diagram. When this has a crack or puncture, it cannot properly open the value anymore and must be replaced on your Chevrolet. The reason the EGR valve and motor helps to improve fuel mileage is to warm the fuel in the combustion chamber before ignition helping for a more complete ignition of it. The exact amount of increased fuel mileage generally is not noticed by a driver and cannot be accounted for in typical fuel mileage calculations because of all the other variables involved in this number. Most drivers of Chevrolets that require a new EGR valve and motor are informed of its malfunction when in inspection of the system is conducted when the vehicle fails an emission test.