What Is the Function of an EGR Valve?

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An EGR valve helps to improve the performance and economy of a vehicle while reducing emissions by directing exhaust gases back into the cylinders of the vehicle for a second burn. The valve reduces nitrous oxide emissions and directs the warmer exhaust back into the engine, reducing the amount of work required by the fuel-and-air mix in maintaining the engine at operating temperature.

The first EGR valves were simple orifices that directed exhaust gas back into the engine. They resulted in several problems, including difficulty starting, poor fuel economy, rough idle and poor performance. Manufacturers redesigned the EGR valve to use the manifold vacuum to keep the valve closed when starting the engine and open it once the engine reached a certain temperature. Although most engines continue to use the EGR valve to meet 2014 emission standards, some manufacturers are finding options that eliminate the valve while still meeting the requirements.

A dirty EGR valve in an engine affects its performance. Many are easy to clean by soaking in carburetor-cleaning fluid. A vehicle owner who attempts this fix should ensure he does not expose electrical connections to the cleaner. Once the device is cleaned and reinstalled, there is usually a noticeable difference in the performance of the engine.