Sticking EGR Valve Symptoms

Written by paul novak
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Sticking EGR Valve Symptoms
Signs an EGR valve is malfunctioning. (exhaust fulmes image by bilderbox from Fotolia.com)

The exhaust gas recirculation (EGR) valve is an integral part of a vehicles emissions control systems. It operates under the premise of lowering combustion chamber temperatures to reduce the amount of pollutants created by the combustion process. Being closely tied to the combustion process, this valve's operation has direct effect on the overall performance of the engine. Poor or faulty operation of the EGR valve can result in several notable symptoms and leads to increased pollutant emissions.

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Poor Idle

An improperly closing EGR valve will act as a vacuum leak, disrupting the correct fuel and air mixture, causing a lean mixture condition. This results in misfiring cylinders and poor engine idle.

Overheating

The basic function of the EGR valve is to introduce exhaust gases into the combustion chamber at specific and controlled rates, lowering combustion temperatures, and lowering pollutant emissions. An EGR valve that does not open properly fails to introduce sufficient amounts of exhaust gases, causing combustion chamber temperatures to rise, leading to overheating of the engine.

Poor Fuel Economy

A sticking EGR valve will not open and close at the proper rate, leading to a reduction in the efficiency of the combustion process due to the lean fuel-air mixture it causes. This results in the engine having to work harder to perform the same amount of work, requiring more fuel to do it. On-board computer systems can also try to compensate for this lean condition by introducing additional fuel to the mixture, further increasing fuel consumption.

Increased Emissions

EGR valves are designed to lower the emission of pollutants from the combustion process. This is done by lowering the temperature of the combustion process through the introduction of exhaust gases into the fuel and air mixture. Lowered combustion temperatures result in more efficient burning of the fuel and air mixture, and less pollutants in the exhaust emissions. An improperly operating EGR valve will not correctly lower combustion temperatures, causing noxious emissions to increase, which can cause a vehicle to fail emissions inspection.

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