EGR Valve Guide

The engine of any car is made up from a number of small components alongside the big ones that we all know about.  These little components all play a vital part in the efficient running of the engine but can break down through the course of doing their job.  One example is the EGR valve or Exhaust Gas Recirculation Valve.  But what is it and how do you know if it needs to be replaced?

EGR Valve

What the EGR valve does

The EGR valve is essentially a simple open and close valve that performs an important function within the car engine.  It does a single job that has a big impact on the smooth running of the engine and the longevity of some of its components – it directs exhaust gases from the combustion chamber or prevents them from entering it.

When the car engine starts up, the valve is activated and is in a closed position, stopping the exhaust gases from flowing.  When the engine reaches the right temperature and is moving at speed, the valve then opens gradually, letting those burning hot gases to enter and combine with the air-fuel mixture in the combustion chamber.  As the car slows, the valve slowly closes once more, blocking the flow of gases.

Valve variations

Petrol and diesel engines have slightly different designs to the EGR valve and different manufacturers also use different styles.  Older model cars may have a small diameter hose that works with the valve, connecting it to the throttle body or the carburettor.  Newer models usually have an electronic vacuum EGR valve within a block or cylinder.  Both work in essentially the same way but the electronic versions have a sensor that communicates with the car’s computer to get better results.

How the EGR valve helps the environment

Not only does the EGR valve play a crucial part in keeping the engine running efficiently but it also helps the environment.  This is because the air that enters the car through the intake manifold is around 80% nitrogen and 20% oxygen.  It combines in the combustion chamber at temperatures over 1300 degrees and the nitrogen gas becomes oxides of nitrogen – the cause of air pollution.

What the EGR valve does it to reduce the temperature of these gases as they leave the engine.  As a result of this, the amount of those nitrogen oxide gas created is reduced and therefore less pollution is released into the atmosphere.

Problems with the EGR valve

The downside of the hard work the valve does is that it can become clogged up or blocked, usually with carbon deposits.  This can result in the valve either sticking open or closed and therefore not functioning properly.

A sign of an open valve is a rough idle when the engine starts or a car that stalls when idling.  It may use more fuel and there might be a slight smell of fuel when running.  It may fail an emissions test or a warning light may appear on the dashboard.  With a closed valve, symptoms are similar.  The main difference is that you will hear a pinging or tapping noise at low RPM.

If you suspect that the car may be having trouble with a blocked or malfunctioning EGR valve, it is important to see a garage as soon as possible to avoid serious damage to the engine.

If you need a replacement used EGR valve you can request one on our car parts request form here.