POST UPDATED IN October, 2021
The EGR valve (Exhaust Gas Recirculation) is a component of the Exhaust Gas Recirculation System, which is located between the intake manifold and the exhaust pipe of vehicles with diesel engines. It serves to reduce the emission of polluting gases such as nitrogen oxide into the environment.
The operation of the EGR system is really simple: it opens and closes the passage to the gases that are going to be recycled. To know when it is time to do the recirculation of gases, the EGR valve and the engine control unit take into account the revolutions per minute of the engine, the amount of fuel that has been injected, what is the volume of air that is entering, the atmospheric pressure and the temperature of the engine.
It stands out therefore, that the EGR valve opens when there is little pressure on the accelerator, the engine is hot and with low revs. In this way, the valve catches the gases and reinserts them through the intake manifold, thus recirculating these gases that are produced by combustion inside the cylinders.
There are two types of EGR valves; pneumatic or mechanical and electronic:
The main problem with the EGR system is the low revolutions, since most of the cars with diesel engines work for a long time with the valve open due to the low speed of revolutions. When the pressure is not reached, char is accumulated and oil residues in the EGR valve, which affects its proper functioning.
Due to the accumulation of dirt, the valve can remain permanently open and recirculate the gases excessively. This in turn will produce a loss of power, jerks in the engine including the exit of a large amount of black smoke through the exhaust.
To prevent this from happening, it is advisable to do the following:
It should be noted that to completely eliminate these failures, some people end up canceling the EGR valve, if it is pneumatic, manually and if it is electronic, through the software, although this is not recommended, since the vehicle could fail to comply the norms that protect the environment.
There are some symptoms, such as low engine performance, considerable increase in fuel consumption, overheating of the engine, emission of dark exhaust smoke, starting with defects.
It is advisable to perform maintenance on the EGR valve every 20,000 km on average and to be carried out by professionals, since buying a new one would be quite expensive. To do this, the gas recirculation system must be completely dismantled and the state of the sleeve communicating the valve with the intake manifold, in addition to the valve body, must be verified.
To clean the EGR valve, it is advisable to use a specialized product, which can be a carburetor cleaner. In case you do not have access to it, you can use KH7 detergent or another that acts in a similar way, in addition to hot or warm water. Try to remove all the dirt that has adhered to the valve and the intake manifold causing both the detergent and the water to circulate throughout the surface and drag all the residues to eliminate them completely.