Everything You Should Know About EGR Valves

March 20, 2025

5 min read

March 20, 2025

5 min read

Not only does the EGR valve reduce emissions, but it also helps the engine run more efficiently. In this quick guide, we explain how the EGR valve works, symptoms of a failing EGR valve, and how to replace it.

The EGR Valve’s Role

A connected EGR valve sitting in the engine of a vehicle. — The EGR valve controls the flow of gasses back into the engine.

EGR stands for “exhaust gas recirculation.” This process takes the engine’s exhaust gasses and redirects them back into the intake manifold to be reused. This system ensures a lower combustion temperature and reduces nitrogen oxide (NOx) emissions for superior efficiency.

What is an EGR valve and what does it do?

The EGR valve is a part of the EGR system, controlling the flow of the gasses back into the engine. It’s an old trick to capture dirty exhaust and re-run it through your engine. The principle is to make cars cleaner. The side effect is that it makes cars run more efficiently.

Early EGR systems arrived when cars were still using carburetors. These engines weren’t nearly as efficient as what’s on the road today. The same is true for their EGR systems. The old ones weren’t nearly as efficient as what you’ll find in the modern fuel injection systems. These external valves are usually mounted to the intake manifold or elsewhere in the exhaust system.

Some newer gas engines no longer use an external EGR valve. Everything is done within the engine. This advanced design allows for more precise management of exhaust gasses. New diesel engines, however, are still equipped with external EGR valves.

When to Replace Your EGR Valve

A mechanic holds an EGR valve removed from the vehicle's engine during a DIY replacement. — Ignoring a faulty EGR valve can cause increased emissions and lead to serious engine damage.

Some manufacturers recommend replacing the EGR valve as preventative maintenance. Check the service schedule to see how often it should be done or replace it every 100,000 miles. You can also clean the EGR valve to keep it working better. This should be done at 50,000 miles or sooner if there’s a problem.

How do you identify a bad EGR valve?

An EGR valve has a simple job: It opens and closes. Malfunction symptoms start to occur when carbon buildup interferes with its ability to open and close. This buildup can cause the EGR valve to be stuck open or stuck closed. Either way, the check engine light likely will come on as a result. The most common trouble codes are P0400 through P0408 and P1403 through P1406.

If you have a faulty EGR valve, it can cause your engine to run rough. You may notice reduced power, lower fuel economy, and a rough idle. Hard starts and engine knock or detonation are also signs of a bad EGR valve.

How long can you drive with a bad EGR valve?

It depends on the symptoms you’re experiencing. If the check engine light is the only problem, you may be tempted to continue driving. However, ignoring a faulty EGR valve can lead to serious engine damage. It can also lead to increased emissions. Neither problem is one you want to deal with. It’s best to have the EGR valve cleaned or replaced at the first sign of failure.

How do you test an EGR valve?

Learning how to test an EGR valve depends on what type of system the car uses.

First, perform a visual inspection. Look for carbon buildup and any sign of damage. Try to move the valve, ensuring it operates freely without getting stuck.
Check if you have a vacuum-operated EGR valve or an electronically-controlled one. A vacuum-operated EGR valve will have a vacuum hose running to it. An electronically-controlled EGR valve will have wires running to it instead.
With a vacuum-operated EGR valve, you need to connect a vacuum pump to the EGR valve’s port. Apply vacuum and monitor the EGR valve for normal movement. If it gets stuck, it’s faulty.
Electronically-controlled EGR valves are checked with an OBDII scanner. Look for EGR-related codes, such as P0401 (EGR flow insufficient). You can activate the EGR valve with a compatible scan tool and listen for any changes in idle speed or engine performance.

Replacing an EGR Valve

Installing a new EGR valve usually takes less than one hour.

Replacing the EGR valve - opens in new window or tab. isn’t normally a complicated job and it only requires a few tools. In most cases, you should be able to finish the replacement within an hour. However, vacuum-controlled EGRs can be more confusing to work on. It’s easy to get vacuum hoses mixed up. They all look the same, and they are not labeled. If your car has a vacuum system, we recommend taking pictures and labeling all of the lines before the replacement to make the reassembly easier.

Not every faulty or stuck EGR valve needs to be replaced. If the EGR valve has less than 50,000 miles on it, you may prefer to try cleaning it.

How do you clean an EGR valve?

Mechanically controlled EGR valves can be cleaned with throttle body or carburetor cleaner, but electronic valves should be cleaned with MAF sensor cleaner. Like MAF sensors, electronically-controlled EGR valves are delicate. Use MAF sensor cleaner because it isn’t as harsh as other parts cleaners.

Simply take off the valve and spray it with the appropriate cleaner. If the buildup is heavy, you may need a stiff brush to get it off. Continue spraying cleaner into the chamber until the fluid changes from brown to clear, indicating that all the buildup has been removed. Before reinstalling the valve with new gaskets, physically operate the valve to ensure it moves smoothly.

How much does an EGR valve cost?

The cost of a new EGR valve is generally between $20 and $100. This price depends on the vehicle’s make and model, as well as if the component is aftermarket or original equipment manufacturer (OEM). High-quality brands may cost more but usually offer a warranty and last longer.

Remember, replacing the EGR valve only takes about an hour on most models of cars. You save a decent amount of money by replacing the EGR valve yourself.

About the author

Brian Jones

Brian worked for several decades as an ASE Certified Master Technician in dealerships before starting his used car lot. Today, he writes for top automotive publications including Motor1. In his spare time, he's dreaming of an escape to the country's best trails in an off-road beast.

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This article is meant to provide general guidance only. Automotive maintenance, repair, upgrade, and installation may depend on vehicle-specifics such as make and model. Always consult your owner's manual, repair guide for specific information for your particular vehicle and consider a licensed auto-care professional's help as well, particularly for advance repairs.