What Are the Symptoms of a Faulty EGR Valve?

What the EGR valve does

The exhaust gas recirculation (EGR) valve sends a small amount of exhaust gas back into the engine. This lowers combustion temperatures and cuts harmful nitrogen oxide emissions. Most diesel cars and many petrol cars have one.

The downside is that exhaust gas carries soot. Over time the soot builds up and the valve can stick open, stick shut or stop moving smoothly.

Common symptoms

Signs of an EGR problem include a rough or lumpy idle, stalling when you pull up, a flat spot or loss of power when accelerating, black smoke, worse fuel economy and the engine management light coming on.

In some cars the engine drops into limp mode, where power is cut back to protect the engine until the fault is fixed.

Why short trips make it worse

Soot builds up fastest on engines that rarely get warm. A car used mostly for short runs around town, like the school run or trips into Birmingham in traffic, is far more likely to have EGR trouble than one that does regular motorway miles.

The same driving habits cause diesel particulate filter (DPF) problems, and the two often go together.

Clean or replace?

If the valve is sticking because of carbon but the motor and sensor inside it still work, a clean can bring it back. If the electrics have failed or the valve is badly worn, replacement is the reliable fix.

Removing or blanking off the EGR valve is not legal on a road car and can mean an MOT failure, so we repair the system rather than remove it.

EGR diagnosis in Smethwick

Other faults can look like a bad EGR valve, such as boost leaks, sensors or injectors. At ER Automotive we test the valve with live data before quoting. Call 0121 461 6097 or book online.