📖 What It Does
Lowers peak combustion temperature by displacing some of the fresh oxygen-rich charge with inert exhaust gas. Cooler combustion means less NOx and, in many cases, slightly better fuel economy at cruise.
⚙ How It Works
At part throttle and cruise, the ECU opens the EGR valve. Hot exhaust gas flows from the exhaust manifold (sometimes through a cooler) into the intake. The diluted charge burns at a lower peak temperature. At idle and full throttle, the valve closes for smooth running and full power.
⚠ Symptoms When It Fails
Carbon buildup is the usual culprit. Symptoms include rough idle, pinging or knocking under load, P0401/P0402 codes, hesitation on acceleration, and failed emissions tests. See full symptom guide.
💰 Replacement Cost
Replacement: $250–$600. A new EGR valve costs $100–$400 in parts. Labor adds $100–$200 depending on accessibility. See replacement cost.
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❓ Frequently Asked Questions
Can I just clean my EGR valve?
Often yes. Many "bad EGR" valves are simply carbon-clogged and work fine after a thorough cleaning.
Will a bad EGR valve hurt the engine?
It can. Sticking open causes rough idle. Sticking closed raises combustion temperatures and can cause detonation.
Does deleting the EGR add power?
A few horsepower at most. It is illegal on street vehicles and will cause CEL.
Why is my EGR valve clogging so often?
Direct-injection engines and short trips both worsen carbon buildup.
Do diesels have EGR too?
Yes, with a cooler. Diesel EGR systems are even more critical to NOx control.
How long does an EGR valve last?
Usually 100,000+ miles on a healthy engine. Less if it carbons up.