​What Does An EGR Valve Do?

Diesel engines use after-treatment emissions reduction systems to reduce their impact on the environment. Without these safeguards, the burning of diesel fuel would release toxic pollutants into the atmosphere, reducing air quality. The Ford Powerstroke engines use what’s known as an exhaust gas recirculation (EGR) cooling system to prevent these gases from escaping through the tailpipe. The cooler lowers the temperature of the incoming air-fuel mixture, which reduces the amount of nitrogen dioxide created during the combustion process.

The EGR is a complicated system that needs regular care and attention, or the internal components will start to break down. A faulty EGR cooler isn’t just bad for the air we breathe; the problem will spread to other areas of the engine once the exhaust-gas mixture overheats. The EGR valve is an integral part of this system. It controls the amount of exhaust gas that is recirculated through the engine, which has a direct effect on the chemical makeup of the air being burned in the combustion chamber. Learn about this central component and how it impacts your vehicle.

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Understanding the EGR Valve

The EGR cooler works by diverting a certain portion of the exhaust gas leaving the combustion chamber away from the exhaust, so it can then be recirculated through the engine. The EGR valve is the sliding vane that controls the process. An opening in the vane allows exhaust gas to pass through, and no exhaust gas can be recirculated when the vane is closed. The size of the opening will vary based on the needs of the engine. Remember that introducing recirculated exhaust gas reduces the amount of heat needed to generate power. The more power the engine needs, the less exhaust gas is recirculated.

It starts out fully closed when the engine is warming up. Once the engine begins to idle, the vane will slide open 90% of the way because the engine needs very little power when idling. As the speed and rotations per minute (RPMs) increase, the valve will begin to close. Not all EGR valves work the same way. Their position and function vary based on the make and model of the vehicle. High-pressure EGR valves divert the incoming exhaust gas to the diesel particulate filter, which removes the particulate matter before it reenters the combustion chamber. Low-pressure valves divert the exhaust after it has already passed through the filter. Digital EGR valves use an electronic feedback system to calculate the exact quantity of exhaust gas needed to power the engine before NOx forms.

Your EGR valve won’t last forever. Most parts will only work for ten years before they start to bite the dust. The valve needs regular lubrication to do its job. You’ll need to change your oil regularly to keep it well-maintained. Excess particulate matter, including ash and soot, can clog the EGR valve as well, which will throw off the amount of exhaust gas being recirculated through the engine. The valve can get stuck in the open or closed position, which will either increase or decrease the amount of heat needed to generate power. If the EGR fails to close at high RPMs, the vehicle will start to lose power. This will lead to increased NOx emissions that can pollute the rest of the vehicle. The diesel particulate filter can start to clog, reducing the flow of fuel.

Once the valve starts to go, you can either replace your EGR system or have the valve cleaned. The part usually needs a thorough wash every 500,000 miles. The diesel particulate filter is responsible for keeping the exhaust gas clean. The EGR valve and filter share a symbiotic relationship. If the filter is dirty, the valve will clog that much more quickly. You are bound to notice a range of problems under the hood once the valve starts to fail. Learn about the bad EGR valve symptoms and how to fix them before the damage gets any worse.

Your diesel engine won’t get far without a working EGR cooling system. The valve on the EGR plays a central role in determining how the fuel and gas are burned in the combustion chamber. Maintain your valve as the miles start to add up to avoid damaging your engine.