Why Does It Fail?

EGR valve failure is typically caused by carbon build-up. Over time, soot and unburned fuel residues accumulate, which can clog the valve or restrict its movement. As a result, the valve may stick open or closed, affecting performance and emissions.

In addition, related components such as EGR coolers, pressure converters, or exhaust gas temperature sensors may also fail. When this happens, they can trigger similar fault codes, making accurate diagnosis essential.

What else could it be? Check for:

• Split hoses and blocked pipes
• EGR coolers (some are separate units)
• Multiple EGR valves (some vehicles will have high/low pressure systems)
• Faulty pressure converters or Exhaust Gas Temperature Sensors

What Are the Symptoms?

A faulty EGR valve can present in two ways:

Stuck Open

• Rough or unstable idle, particularly when the engine is cold

• Stalling at idle

• Poor fuel economy along with a strong fuel odour

• Excessive emissions, often resulting in MOT failure

Stuck Closed

• Engine knock or detonation, especially at low RPM

• Increased NOx emissions, raising the risk of MOT failure

• Potential for serious engine damage due to uncontrolled pre-ignition

In both scenarios, the Check Engine Light (MIL) may illuminate. However, it’s crucial to carry out a full system diagnosis—not just rely on the fault code—in order to identify the true cause.

Fitting Tips

Getting the replacement right means going beyond just the part:

Clean the System Thoroughly

• Use an EGR or turbo cleaner to remove carbon deposits.
• Clean intake ducting, turbo vanes, and consider a professional decarbonisation service if contamination is severe.
• Always replace the air filter.

Fit the New EGR Valve

• Once the system is clean and dry, install the new component.

Reset the ECU

• Complete an ECU reset or drive cycle to allow the system to recalibrate. Some vehicles require dealer-level tools (e.g. VCDS for VAG models).