What is an EGR valve and what does it do?

EGR valve and what does..

Within modern internal combustion engines, Exhaust Gas Recirculation (EGR) is a method to control Nitrogen Oxides (NOx) emissions, produced as a by-product during the combustion process.

Air from the environment, mostly a combination of Oxygen and Nitrogen, combines with fuel and ignites inside the combustion chamber, temperatures increase and produce NOx emissions.

The EGR system works by returning a small portion of exhaust gas to the engine’s combustion chambers through the intake manifold, lowering combustion temperatures and therefore reducing the amount of NOx emitted.

Modern cars use an electronically controlled EGR valve, where the valve receives input from the car’s Engine Control Unit (ECU). These are more sophisticated and use sensors to gauge how much exhaust to let in and when, creating greater emissions reduction and efficiency.

Here are a few common symptoms of a failing or blocked EGR:

• Check Engine light is on: This can obviously happen for many other reasons, but in this case the engine computer has detected the valve is malfunctioning.
• Black exhaust smoke/fuel smell in and around the vehicle: This is a sign that unburnt fuel is exiting through the exhaust pipe.
• Decreased engine power/stalling at low speeds: This happens when too much exhaust gas is flowing into the cylinders at the wrong time.
• Rough idle: When your engine is cold, a rough idle is caused by the EGR valve getting stuck open and causing the temperature in the cylinder to get too low. If it’s idling rough after it’s warmed up, it’s a symptom of an EGR valve that’s stuck closed – however you’d expect to see an engine light on with these symptoms.
• Engine knocking noises: This is due to increased temperatures in the cylinder, causing fuel to ignite when it shouldn’t. Current engine computers will detect this early and throw and engine light.
• Reduced fuel economy: If the EGR is faulty, it can mean lower temperatures in the engine, meaning that the fuel is not being ignited efficiently.
• Failed emissions test: As the EGR is an emission reduction device, if it isn’t working properly your vehicle won’t pass an emissions test and will throw an engine light.

If your car isn’t running properly or experiencing any of the above symptoms and you suspect a faulty or blocked EGR valve, visit any Autobahn location and our professional technicians will diagnose and advise on the best solution to fix the fault..