EGR valve: what it is and what it is for

The EGR valve is a mandatory component in both diesel and petrol engines, whose function is to retain harmful particles produced by burning fuel

The automotive industry has been improving the efficiency of fuel use and, at the same time, incorporating new technologies or components that reduce the consumption and impact of burning fuel.

In fact, one of the areas where the greatest effort has been made in recent years is the reduction of polluting gases that contribute to the greenhouse effect and are harmful to the environment and, therefore, to health, such as the dreaded nitrogen oxides, known as NOx.

What the EGR valve is and where it is located

Among the priority anti-pollution measures for cars with combustion engines, whether diesel or petrol, the capture and neutralisation of these molecules is the job of, among other components, the EGR valve, a part that is present and mandatory in cars manufactured for about the last two decades.

This component is located between the intake manifold and the exhaust manifold. Its location is due to the fact that the engine takes in outside air for burning fuel, and this combustion generates, among other residues, NOx molecules.

The flow of gases towards the exhaust manifold, still carrying unburnt fuel particles, forces the mixture to pass through the EGR valve, where, thanks to its membrane, or its two membranes depending on the type, these particles are retained and reintroduced into the engine, where they should be eliminated by combustion, a process similar to that carried out by the particulate filter.

This means that the function of the EGR valve is, fundamentally, to recirculate exhaust gases, taking the mixture from the exhaust gases and reintroducing it into the combustion chamber through the intake manifolds, hence its name, in English, exhaust gas recirculation valve.

EGR maintenance and faults

Due to its use and function, it is advisable to monitor and maintain the EGR valve. To do this, the routine should involve inspecting and cleaning the device at intervals of less than 10,000 kilometres or, at least, once a year, in order to avoid premature wear or faults.

One of the recommended routines in EGR maintenance is to regularly perform, with the engine and fluids hot, some accelerations close to the rev limit while the vehicle is in motion, so that the burning and elimination of these residues is encouraged.

The very high temperatures that can be reached in an engine block allow these residues from the device to be incinerated in a way that is almost imperceptible to the occupants of the car; only a smell of carbon might hint that this cleaning is taking place.

To avoid EGR problems, it is advisable to visually inspect the build-up of impurities or carbon deposits inside it by removing it, a process that, in most cases, is simple. Build-up can cause it to malfunction or become blocked.

Some of the signs that may indicate a fault in the EGR valve include jerking, misfiring, engine stalling, fuel consumption above normal, excessive smoke, loss of power and, likewise, emissions levels not permitted at the MOT (ITV), which results in failing the inspection itself.

There are specific products that clean these residues and remove the deposits adhered to the valve. These liquids are highly polluting and need to be treated, so their cleaning must be carried out at an authorised point, such as a mechanic’s workshop. This can be a first resort if you have problems with the EGR, but if they are not resolved, the situation could be more serious.

If the embedded dirt cannot be removed by these means, it may have caused greater damage to the springs that allow the gases to enter or to the membrane or membranes that filter and retain the particles. In that case, it would be necessary to replace the device itself.