THE EGR VALVE: TECHNICAL EXPLANATIONS AND CARE TIPS

Invented in the United States in the 1970s and tested by Generals Motors to reduce NOx (Nitrogen Oxide) emissions, the EGR (Exhaust Gas Recirculation) valve has been made compulsory on recent diesel engines by European pollution control standards which, since 2015, have imposed a maximum emission rate of 80mg/km (compared to 180mg/km in 2009).

The EGR valve is therefore a system that eliminates the toxic gas particles produced by the engine by reinjecting part of the exhaust gases into the inlet. Depending on the engine type, the amount of gas reinjected varies from 5 to 35%.

When a diesel engine is idling or running at low speed (2,500 rpm), part of the exhaust gas is not completely burnt, resulting in the release of excess nitrogen oxide and fine particles into the atmosphere.

To minimize these emissions, which are contrary to European standards, the manufacturers have installed a valve part that redirects these exhaust gases to the injection system so that they are burned a second time before being cooled. This second combustion mechanically reduces the fine-particle content.

Although effective in controlling the Nox emission rate, this system has the disadvantage of creating soot, which eventually clogs the injection system and the valve itself. Indeed, if the clogged valve stays closed, the vehicle will run normally but will pollute more. Conversely, if the valve remains permanently open, it could drastically damage your car’s inlet system. For this reason, you should care for your EGR system regularly by taking the right steps and actions.

Power loss, engine light, black smoke, etc.: if you notice any of these symptoms, your EGR valve is probably damaged. Don’t panic, before considering replacing it, there are a few simple things you can do to clear it.

Indeed, EGR valve failure usually occurs as a result of short daily trips at low speed with a cold engine. For this reason, we recommend that you drive on the motorway at high speed at about 130 km/hour, or about 3,000 revolutions per minute, for 15 minutes to burn off the carbon that builds up in the system. You can also completely clean your EGR valve regularly using a specific, appropriate product to be injected into the fuel tank.