An EGR valve is found almost exclusively in diesel engines. This system was first tested by General Motors. This happened as early as 1970 and it has been a widely used technique ever since. The valve helps to reduce the emission of toxic substances from the atmosphere. Unfortunately, a dirty EGR valve can cause malfunctions. In this case, it can be cleaned or removed completely. After reading this article, you will know how an EGR valve works, how to maintain it and whether removing it is wise. 


The term EGR valve stands for exhaust gas recirculation. General Motors first tested this system in 1970. It recirculates spent exhaust gases back into the air intake of an engine. This is also one of the reasons why the EGR valve can become contaminated. 

The system is controlled by the central computer of the car. Depending on the manufacturer, the valve is opened at a certain speed, for example 2000 rpm. 

The engine computer controls the EGR valve via a solenoid valve or an electric valve, depending on various parameters (water temperature, air temperature, engine load data, etc.).

By reusing the exhaust gases, the emissions (NOx) are reduced by 10 to 40%. This depends on the engine and the engine management. Each manufacturer has to comply with the emission regulations of the respective country, the engine management is adjusted accordingly.  

Disadvantage of an EGR valve

The engine emits an excess of nitrogen oxide and small particles into the atmosphere, which violates European emission standards. In an attempt to reduce such emissions, manufacturers install the EGR valve, which directs exhaust gas back to the injection so that it burns a second time. Unfortunately, this process creates excess hydrocarbons in the form of soot, which accumulates in the EGR system and sometimes clogs it up completely; this can affect the rest of the engine. The engine no longer functions as it should because of the unburnt gases that are injected into it. The EGR valve starts to malfunction when it is clogged; carbon emissions (soot) accumulate in the valve and restrict the mobility of the solenoid or the valve, which can lead to a complete blockage. The system fails and the engine computer switches to a lower operating mode, causing a significant loss of power.

A permanently open valve can damage your intake system. It is therefore important to regularly service the EGR valve of your diesel. Otherwise it can become a recurring problem. 

Symptoms of a defective EGR valve:

  • Power loss
  • Engine management light on (emission fault)
  • Black clouds of smoke when accelerating rapidly
  • A faltering car 

EGR valve removal

Although it is not permitted to remove or cap the EGR valve, in some cases it is the only way to get the car to function normally again. In extreme cases, you can also install a new valve, but this can be a costly affair. 

However, because it is not allowed, problems can arise during the MOT, the so-called soot measurement will show too high values, resulting in a car being rejected. Besides a complete replacement, cleaning can also work, although there is a chance that the problem will return in time. 
Finally, driving many short distances can also have a detrimental effect on the EGR valve, which is why, as with the soot filter It is wise to drive long distances at times.