Hobbies Cars & Motorcycles What an EGR Valve Does and When It Should Be Repaired Share PINTEREST Email Print birdlkportfolio/Getty Images Cars & Motorcycles Cars How Tos Buying & Selling Basics Reviews Tools & Products Classic Cars Exotic Cars Corvettes Mustangs Tires & Wheels Motorcycles Used Cars SUVs Trucks ATVs & Off Road Public Transportation By Matthew Wright Matthew Wright has been a freelance writer and editor for over 10 years and an automotive repair professional for three decades specializing in European vintage vehicles. our editorial process Matthew Wright Updated February 02, 2018 The exhaust gas recirculation (EGR) valve helps your car more efficiently and completely burn the car's fuel by recirculating a portion of your exhaust and running it through the combustion process again. This results in a cooler, more complete burn of the fuel which decreases your car's noxious emissions by prohibiting the formation of some harmful gasses. If your EGR valve is faulty or clogged, your engine starts to run badly. You also begin to pollute the atmosphere with exhaust gasses that your car is normally not dumping into the air. Regardless of your motivation -- economical or ecological -- a faulty EGR valve should be cleaned or replaced as soon as possible. If you're still interested in learning about your EGR valve, you'll find some helpful info below, along with a little troubleshooting help if you think your valve is bad or on its way out. Pros of an EGR Valve The EGR valve is vital to your car's emission controls. Exhaust gas recirculation helps to keep huge amounts of unburned fuel from being released into the atmosphere. This unburned fuel is thought to be a huge contributor to greenhouse gas build-up. That's why an EGR system became mandatory on all new vehicles some time ago. Cons of an EGR Valve When the EGR valve goes bad, it must be replaced. Unlike some emissions control devices that can go bad without affecting the drivability of the car or truck, a bad EGR valve can really affect the engine's performance or even cause it to stop running altogether. The good news is you can clean it. How to Know If Your EGR Valve Is Stuck or Malfunctioning The EGR valve, or Exhaust Gas Recirculation valve, is a vacuum controlled valve which allows a specific amount of your exhaust back into the intake manifold. This exhaust mixes with the intake air and actually cools the combustion process. Cooler is always better inside your engine. The exhaust your EGR valve recirculates also prevents the formation of Nitrogen related gasses. These are referred to as NOX emissions and are a common cause for failing emissions testing. Unfortunately, your EGR valve can get stuck, causing NOX gasses to build up. You'll know if your EGR valve is stuck or malfunctioning because your car will experience symptoms like rough idle and bucking on acceleration. Fuel mileage will also suffer, and you may see a check engine light followed by a readable code in your car's OBD-II or newer computer. Cleaning vs. Replacing an EGR Valve If you're considering the choice of whether to clean your EGR valve or simply replace it to get your emissions control system back up and running (and pass your state's vehicle inspection or emissions testing!), you need to do a little cost analysis. An EGR valve for your car is relatively inexpensive, so it may be well worth installing the new part if you can afford to.