EGR valve, everything you need to know: how it works and the types of valves that exist

The letters EGR stand for Exhaust Gas Recirculation, that is, the recirculation of exhaust gases. Its main function is to reduce nitrogen oxide emissions (NOx) so that the car pollutes less and complies with current regulations. To achieve this, part of the gases that leave through the exhaust is redirected back into the intake circuit.

Physically, it is a duct that connects the exhaust with the intake manifold so that the gases return to the combustion chamber instead of being expelled outside. A valve allows a quantity of gas set by the engine control unit to pass through. During this process, the temperature is reduced and therefore emissions are lowered.

How the EGR valve works

The operation of the EGR system is quite simple and works like any valve: it opens and closes the passage for the gases that are to be recycled. To determine when gas recirculation should take place, the EGR valve and the engine control unit take into account several variables: engine speed, amount of fuel injected, volume of air at that moment, atmospheric pressure and engine temperature.

It is therefore worth noting that the EGR valve opens when light pressure is applied to the accelerator, the engine is warm and running at low revs. In this way the valve captures the gases and reintroduces them through the intake manifold, thereby carrying out the recirculation of these gases produced by combustion inside the cylinders.

Types of EGR valves

Although, chronologically, up to 6 different types of valves can be found since their introduction in the 1970s, today the market offers two types of EGR valves: pneumatic or mechanical ones and electronic ones, which meter the flow of recycled exhaust gases.

• Pneumatic or mechanical valve: these were the first to be used and are operated by a vacuum or depression system through a solenoid valve controlled by the engine’s electronics.
• Electronic valve: they work on a system similar to that of the electronic pumps in direct-injection diesel cars and are fully autonomous. They incorporate sensors to verify that the system is working normally within the established parameters.

How to tell if the EGR valve is failing

A fault in the EGR valve is not easy to detect, nor is it noticed quickly. Most valves cannot self-diagnose faults, unlike the battery or engine oil level, which the dashboard warns you about in any vehicle.

For this reason, we recommend that you listen to your car to check whether any of these symptoms of a malfunctioning valve appear:

• Starting problems.
• Jerking when accelerating.
• Increased fuel consumption.
• The engine stalls.
• Reduced power
• Excessive smoke.
• Strange and unfamiliar noises.

Keep in mind that EGR valve problems are more common in diesel engines than petrol ones because they generate more soot, which adheres to the valve walls and intake manifolds. The result? The vehicle gradually loses performance.

What can I do to avoid EGR valve problems

To clean and remove the soot from our car’s engine, we can follow a series of tips that will greatly help reduce the black smoke expelled from the exhaust pipe.
First of all, it is advisable to drive normally for a few minutes so that the engine reaches its optimal operating condition. Then you should rev it to around 3,000 or 3,500 rpm, so that the exhaust gases come out with enough force to clean the soot from the inside. The best way to do this is to drive on the motorway for five or ten minutes.

At that speed, enough air will flow through the radiator so that we don’t cause unnecessary overheating by running at such high revs. It is good to do this periodically, once a month, for example, and even more so if the car is normally driven in the city.

One of the first benefits we will notice from this operation is that our car will feel looser and more lively. We will also notice that fuel consumption is lower, which our wallet will surely appreciate.

How much does a new EGR valve cost?

If we have exhausted the previous option and our EGR valve is clogged with soot, we have no choice but to go to the workshop, replace it and solve the problem, after a stop at the cash desk, of course. This is the most logical option, but also the most expensive, as it could cost up to 900 euros depending on the brand, far above the average price in Spain of 350 euros.

Another, less recommended option is deleting this EGR valve, because it will only be useful in very specific cases and could result in a fine and failure to pass the MOT/roadworthiness test.

Can the EGR valve be deleted? Advantages and disadvantages of doing so

When we accelerate with the engine at low or medium revs, this valve opens. In those moments of low demand, the loss of performance caused by recirculating burnt gases with less oxygen is less noticeable. When accelerating hard and the engine revs up, the valve closes so that only fresh air enters the mixture, increasing performance and therefore combustion temperature, which produces more nitrogen oxide.

As we have mentioned, some users decide to delete it to achieve more power when the car is running at low and medium revs. In terms of pure performance there will be no benefit, because when accelerating hard the valve remains closed.

Deleting it could also bring lower consumption in the long run, since it improves performance at low revs and, by not recirculating burnt gases, prevents impurities from building up in the cylinder ducts and valves, which would otherwise reduce engine efficiency.

However, deleting the EGR valve does not only have advantages; its disadvantages can end up being very costly:

• Higher emissions of polluting gases in the range where the diesel engine is most used.
• The car is likely to fail the MOT/roadworthiness test due to excessive pollution.
• More noise and roughness at low and medium revs, because the engine and its injection are designed to operate with a portion of burnt gases. Therefore, if we delete this valve, the engine will only receive fresh air at low revs.
• The engine takes much longer to reach its ideal temperature and, as a result, cold consumption increases.