Mechanic (Pneumatic) EGR valve and Electric EGR (Exhaust Gas Recirculation) valves recirculate a portion of the exhaust gas from the engine (5% to 15%) back into the combustion process. This ensures that the fuel is completely burned while decreasing the emission of harmful gases such as nitrous oxide. Some indications that your EGR valve is becoming faulty are an increase in exhaust particles, rough idling & misfiring and hard starting. When replacing the EGR valve, the valve is not always as accessible in each model of vehicle. A helpful tip when fitting the new valve is to wrap a small piece of plastic around the socket of your wrench and then insert the bolt in to the socket. By doing this, it wedges the bolt in the socket allowing you to fit the valve without dropping these essential fitment components in to the engine bay.