EGR Valve is a very essential part of the modern vehicles because it controls the NOx emissions and the combustion of the engine. That happens by adding a small amount of the exhaust gases of the engine, back to the intake manifold of the engine in order to achieve lower combustion temperature. NOx are produced when the the Nitrogen included in the air, is joint with oxygen. That only happens when combustion temperature exceeds 1500 degrees Celsius.

The first part of the EGR System is the Exhaust Gas-Recirculation Valve which is controlled by intake vacuum and is positioned on the intake. The second part is an electrovalve which is either adapted to the Exhaust Gas-Recirculation Valve or in a separate position.

A malfunctioning EGR Valve will cause the engine to have an unstable idle and a significantly reduced amount of power.