The EGR valve is vital to your car’s emission control; it controls a small passageway between the intake and exhaust manifolds. The EGR valve, or Exhaust Gas Recirculation valve, is a vacuum controlled valve which allows a specific amount of your exhaust gas back into the intake manifold. When the valve opens, intake vacuum draws exhaust gases through the valve. 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. The EGR valve helps your car run more efficiently and completely burn fuel by recirculating a portion of your exhaust gases and running it through the combustion process again. That’s why an EGR system became mandatory on all new vehicles some time ago. When the EGR valve malfunctions, it must be replaced. Unlike some emission control devices that can malfunction without affecting the performance of the vehicle, a faulty EGR valve can really affect the engine’s performance, or even cause it to stop running altogether. This exhaust gas mixes with the intake air and actually cools the combustion process. Cooler is always better inside your engine. The exhaust gases that your EGR valve recirculates also prevents the formation of Nitrogen related gases. 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 gases 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. EGR valves do not normally require maintenance or replacement for preventative maintenance, but the valve can become clogged with carbon deposits that cause it to stick or prevent it from closing properly. Dirty EGR valves can sometimes be cleaned, but replacement is necessary if the valve is defective.