EGR Valve Problems: Signs, Causes and Fixes

What the EGR valve does

EGR stands for exhaust gas recirculation. The EGR valve lets a small, controlled amount of exhaust gas back into the engine intake. This lowers the combustion temperature, which cuts the harmful nitrogen oxides the engine produces.

Most modern diesels have one, and many petrol engines do too. The engine computer opens and closes the valve depending on how you are driving, so it is working away all the time without you knowing.

Some cars also have an EGR cooler, which cools the exhaust gas before it goes back into the engine. The cooler can block up with soot or, less often, leak coolant, so we check it too when we are looking at EGR problems.

Why they go wrong

Exhaust gas carries soot and carbon. Over time this sticks to the valve and the pipes around it, and slowly builds into a hard, tarry layer. Eventually the valve can stick open, stick shut or not move freely.

Short trips make it worse, as the engine rarely gets hot enough to burn deposits off. Many EGR valves are electrically operated too, so a failed motor, sensor or wiring fault can stop the valve working even when it is clean.

Signs of a faulty EGR valve

A sticking EGR valve can cause a lumpy or rough idle, hesitation or flat spots when you accelerate, and a general loss of power. Some cars go into limp mode to protect themselves.

You may also see more black smoke than usual from a diesel, notice the fuel economy getting worse, or have the engine management light come on. On some diesels, a faulty EGR valve can also lead to DPF problems, because the extra soot fills the filter faster.

These symptoms are shared with lots of other faults, from injectors to air leaks and sensors, so it is not safe to assume the EGR valve is to blame without testing.

How we diagnose it

We start by plugging in our diagnostic equipment to read any fault codes and watch live data while the engine runs. That shows us whether the valve is doing what the engine computer is asking it to.

If the evidence points to the EGR system, we can test the valve itself and inspect it for carbon build-up. We only recommend a repair once we are confident of the cause, so you are not paying for parts that do not fix the problem.

Clean or replace?

If the valve is mechanically sound and simply clogged, cleaning it can bring it back to life. If the motor or sensor has failed, or the valve is badly worn, replacing it is the better fix. Some valves are built in a way that makes cleaning impractical.

Either way, we will tell you which option suits your car, what it involves and give you a quote before any work starts. As with a DPF, we do not blank off or remove EGR valves. It can cause the car to fail its emissions requirements and we keep every car we work on road legal.

Get it sorted early

Regular servicing and a good run on faster roads now and then help keep carbon at bay. If your car has started to feel flat or rough, the sooner it is checked, the less chance it has of causing other problems.

Call us on 01922 682200 or book online, and bring it to us at 45 High Street, Pelsall.