8 Critical Symptoms of a Bad EGR Valve (+ How to Prevent It)

Have you been noticing poor engine performance and increased fuel consumption?
Did your vehicle fail its emissions test too?

Chances are you have a faulty EGR valve.
The EGR valve is an often overlooked component in your vehicle’s Exhaust Gas Recirculation or EGR system.

Keep reading to find out how an EGR valve works and the common signs of a malfunctioning EGR valve so you can spot it before it’s too late.

This Article Contains

What Is an EGR Valve and How Does It Work?
8 Alarming Symptoms of a Bad EGR Valve
What Causes EGR Valve Failure?
Can I Drive With a Faulty EGR Valve?
How to Prevent EGR Valve Failure?
3 FAQs about the EGR Valve

What Is an EGR Valve and How Does It Work?

An engine’s ignition and combustion process requires a precise air-fuel mixture to power the pistons. However, this process generates a lot of heat and harmful nitrogen oxide (NOx) emissions.

The exhaust gas recirculation valve (EGR valve) redirects some of these exhaust gasses back into the combustion chambers to reduce your car’s nitrogen oxide (NOx) emission.

Here’s how it functions:

The EGR valve operates in two main settings:

It stays closed when the engine starts
It opens when it’s idling or running at low speeds

When the engine is under partial load, like during idling, the Engine Control Module (ECM) signals the EGR valve to open. This allows the exhaust gasses to mix with fresh air and fuel in the intake manifold before entering the combustion chamber.

Now, exhaust gasses don’t burn like fresh air-fuel mix. There is a lesser concentration of oxygen in the exhaust gasses, which helps lower the peak combustion temperature. Since NOx usually forms at high temperatures during combustion, the introduction of inert exhaust gasses helps reduce NOx emissions.

Wondering how to spot a failed EGR valve?
Let’s find out.

8 Alarming Symptoms of a Bad EGR Valve

When the exhaust gas recirculation valve fails, there are two ways it can happen:

It stays stuck open: Allowing exhaust gas to enter the engine at the wrong time.
It stays stuck closed: Preventing exhaust gas from entering the engine.

But how do you know if it’s stuck in an open or closed position?
Here are eight common symptoms of a faulty EGR valve to help you figure it out:

1. Rough Engine Idle

The first sign of a failing EGR valve is when your vehicle undergoes a rough idle, either when starting the engine or during brief stops.

It usually happens when the EGR valve stays stuck open, causing a continuous flow of exhaust gasses (also called an EGR flow) into the intake manifold. This disrupts the air-fuel mixture in the combustion chamber, leading to inefficient combustion and a rough idle.

2. Engine Knocking or Pinging Sounds

When the EGR valve is stuck closed, it prevents the recirculation of exhaust gasses. Consequently, the temperature in the combustion chamber keeps rising and exceeds the threshold for proper combustion.

As a result, the fuel ignites earlier than it should, especially at low RPMs. This untimely fuel combustion may cause engine knocking or a pinging sound.

Note: Ignoring this symptom can also damage other vehicle components, like the spark plugs.

3. Smell of Fuel

When the valve isn’t working correctly, your engine will likely burn more fuel than it should. This causes your engine to release more unburnt hydrocarbons in the exhaust emissions. As a result, you may notice a fuel smell in the cabin and decreased fuel efficiency.

4. Increased Fuel Consumption

The exhaust gas recirculation valve opens and closes based on the throttle movement and exhaust manifold vacuum. When carbon deposits build up in the valve, the EGR valve can stay stuck open, allowing exhaust gas to re-enter the combustion chamber at the wrong time.

It can also result in a vacuum leak in vacuum-operated EGR systems. This again affects the fuel economy as the engine tries to compensate by increasing fuel consumption.

5. Increased Emissions

A functional exhaust gas recirculation valve helps reduce NOx emissions from your car’s exhaust fumes. However, a faulty valve can have the exact opposite effect.

This can happen in two ways:

Stuck open EGR valve: Lowers the temperature inside the combustion chamber and prevents proper fuel combustion, releasing more unburnt hydrocarbons in the exhaust fumes.

Stuck closed EGR valve: Raises the combustion temperature and your car has a higher concentration of NOx emissions in the exhaust fumes.

That’s why increased vehicle emissions caused by an EGR valve problem can make your vehicle fail an emissions test.

6. Reduced Engine Performance

Driving with a faulty EGR valve can reduce engine performance, especially when accelerating.

This happens when your engine operates with an incorrect air-fuel mixture. The ECU overcompensates with more fuel to maintain power output, leading to decreased fuel efficiency.

Conversely, if the valve is stuck open, your car may take longer to reach higher speeds. In severe cases, the engine might even shut off unexpectedly while driving.

7. Engine Overheating

A malfunctioning EGR valve can contribute to engine overheating, especially when stuck closed.

If the EGR valve is stuck closed, it can’t regulate the EGR flow and redirect the exhaust gasses back into the combustion chamber to burn along with the fresh fuel mixture. This increases the oxygen concentration in the chamber, causing the engine to burn more fuel and thereby raising the engine temperature.

8. Illuminated Check Engine Light

A clogged or faulty EGR valve can trigger the Check Engine Light. This is common in vehicles with an electronically controlled EGR valve, as the Engine Control Unit (ECU) directly controls the valve’s movement. If the Check Engine Light comes on with the above-mentioned symptoms, you might have a failing EGR valve.

To confirm if the warning light is on due to EGR issues, look for these diagnostic trouble codes (DTC):

P0400: Exhaust Gas Recirculation (EGR) Flow Malfunction
P0401: Exhaust Gas Recirculation Flow Insufficient Detected
P0402: Exhaust Gas Recirculation “A” Flow Excessive Detected

Note: Engine problems resulting from a malfunctioning EGR valve can also be caused by other car parts and sensors. For example, increased hydrocarbon emissions can result from a leaking fuel injector, a bad catalytic converter, or a faulty oxygen sensor. That’s why you should consult a mechanic for a proper diagnosis.

But why does the EGR valve fail?
Find out next.

What Causes EGR Valve Failure?

Several factors can cause the EGR valve to malfunction, including:

Use of low-quality or contaminated fuel
Lack of regular engine maintenance
Faults or malfunctions in the EGR system
Manufacturing defects or low-quality parts
Extreme driving conditions

Next, let’s find out if you can continue driving with an EGR valve problem.

Can I Drive With a Faulty EGR Valve?

No, driving with a bad EGR valve isn’t recommended.

While you can safely take your car to the nearest repair shop, driving for extended periods with an EGR failure can lead to reduced engine power, poor acceleration, and vehicle stalling. If left unchecked, it can cause serious engine damage.

Want to keep your EGR valve from failing?
Keep scrolling!

How to Prevent EGR Valve Failure?

Follow these tips to prolong the life of your EGR valve:

Use a high-quality fuel your car manufacturer recommends and add additives to prevent carbon deposit buildup in the EGR passage.

Get regular auto repair and maintenance checks, including oil changes and fuel filter replacements.

Monitor your engine’s performance and fuel efficiency. If you notice a decline, get your EGR system inspected.

Clean or replace the faulty EGR valve to prevent carbon buildup from clogging the EGR pipe.

Note: Diesel engine cars with EGR coolers may require a coolant top-up, as mechanics usually drain some of it during valve maintenance or when replacing the EGR cooler.

Have more questions?
Check out the following FAQs.

3 FAQs about the EGR Valve

Here are the answers to some common queries related to the exhaust gas recirculation valve:

1. How Long Does an EGR Valve Last?

An EGR valve typically lasts ten years with routine maintenance and checks. However, it’s best to refer to the owner’s manual for specific replacement intervals for your car model.

You can also consider replacing it if there’s physical damage or an identified EGR problem.

2. How Much Does an EGR Valve Replacement Cost?

You can expect to pay between $100 to $1,000 or even more for an EGR valve replacement.

The actual cost of replacing an EGR valve depends on your vehicle’s make and model, labor charges in your area, repair complexity, and part costs.

3. Can I Clean the EGR Valve Without Removing It?

Yes, you can clean your EGR valve without removing it using an EGR valve cleaner spray. You’ll have to spray it directly into the engine while it’s running at about 2,000 RPMs and follow its application instructions carefully.

Remember, this cleaner comes in different versions for a petrol or diesel engine, so ensure you pick the one compatible with your car’s engine.

And if you lack the knowledge and skills needed to access engine parts, it’s best to hire a professional mechanic — especially if the valve is completely stuck.

Fix Your Bad EGR Valve with AutoNation Mobile Service

Your vehicle’s exhaust gas recirculation valve reduces harmful nitrogen oxide emissions and improves engine performance. Identifying and diagnosing the symptoms of a bad EGR valve early can help you address the EGR problem sooner and avoid costly repairs.

And if you have a faulty EGR valve, rather than attempting a DIY fix, get immediate help from professionals like AutoNation Mobile Service.

We’re a mobile auto repair service available seven days a week. We offer easy online booking and a 12-month | 12,000-mile repair warranty.