EGR valve
A valve that feeds a small amount of exhaust back into the engine to cool combustion and cut polluting emissions.
In plain English
EGR stands for exhaust gas recirculation. The EGR valve sits between the engine's exhaust side and its air intake, and when it opens it lets a measured bit of spent exhaust flow back in with the fresh air. That exhaust no longer burns, so it lowers the peak temperature inside the engine, which reduces nitrogen oxides (NOx), a type of air pollution. On newer cars the engine computer decides when and how far the valve opens; older cars use engine vacuum to move it.
Why it's on your estimate
Exhaust carries soot, and over time it can build up as hard carbon inside the valve and its passages, making the valve stick open or shut. A valve stuck open tends to cause a rough or shaky idle, hesitation, and stalling, while a valve stuck shut can cause a pinging or knocking sound when you accelerate and higher emissions. Either way the check engine light often comes on, fuel economy can drop, and the car may fail an emissions test.
How urgent is it?
Fix soon
Many cars with an EGR problem can still be driven carefully for a short time, but the problem usually gets worse rather than better. It becomes more serious if the engine stalls in traffic, knocks or pings under load, or the check engine light flashes, since ongoing knocking or misfiring can damage the engine.
Questions to ask the shop
- What trouble code or test shows the EGR valve itself is the problem, rather than a clogged passage, a vacuum leak, or a wiring fault?
- Can the valve be cleaned, or is it too clogged or damaged and needs to be replaced?
- Do the EGR passages also need cleaning so the new or cleaned valve does not clog again right away?
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