What Is An EGR Valve?

What is an EGR valve, and how does it work?

“EGR” stands for exhaust gas recirculation. When engine combustion temperatures near 2500°F, the formation of smog-producing nitrogen oxides (NOx) increases. Exhaust, however, is mostly composed of carbon dioxide (CO2), which does not burn. The function of the EGR valve is to recirculate small amounts of exhaust back into the combustion chambers of the engine in order to decrease the combustion temperature, thereby reducing the formation of smog-producing nitrogen oxides. EGR valves can malfunction by becoming stuck open or closed due to carbon buildup. When an EGR valve malfunctions, CO2 is reintroduced to the combustion chamber at the incorrect time or in incorrect amounts, which does not decrease the combustion temperature sufficiently enough to prevent the increase of NOx. Often times, EGR Valves are replaced unnecessarily due to clogged EGR ports that need to be cleaned. Many times cleaning the EGR ports alone will resolve concerns.

When does an EGR valve need to be replaced?

Symptoms of a malfunctioning EGR valve include:

  • Check Engine Light is on for an EGR fault and ports are confirmed clean
  • Pinging and/or knocking sounds
  • Rough idle
  • Reduced power
  • Reduced fuel economy
  • Engine stalling/hesitation when accelerating

Tools + Parts Checklist:

How To Replace EGR Valve

  1. Put the vehicle in park and apply the emergency brake. Consult your owner’s/repair manual to locate the EGR valve.
  2. Turn off the engine and disconnect the battery.
  3. Inspect all vacuum lines for rips, tears, and holes. Replace as necessary.
  4. Remove the vacuum line or unplug the electrical connector from the EGR valve.
  5. Remove the bolts that hold the EGR valve to the cylinder head or intake manifold.
  6. Remove the EGR valve. Be careful to protect the open cylinder head or intake manifold from any debris. Tech Tip: Clean the EGR ports while you are this far into the system (reference this article to learn how to clean the EGR ports while you’re in there)
  7. Bolt on the new EGR valve and attach the vacuum line or plug in the electrical connector.
  8. Reconnect the battery.
  9. Start the car and use the diagnostic tool to check for any codes and reset the check engine light.
  10. Do a test drive to ensure the engine is running and idling smoothly.

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  1. Thanks a lot for this information

  2. I just replaced my egr valve yet it cracked again why is that

  3. Can the erg valve be cleaned

    1. Hey Laura! Yes you can clean an EGR valve!

      FIXD Team

      1. What do you clean it with?

  4. This was helpful I do have a check engine light the code is reading knock sensor bay one I replaced #2 knock sensor about 3 months ago the code never when tout but I think it switched knock sensor any way they have both been replaced I don’t see any frayed wires any where. I did notice there is a snow flake right beside the obd code I got FIXD obdi read somewhere that it could have something to do with the coolant not circulating how can I figure that out?yes,it has anti freeze The truck has never over heated but it really idles ruff and buried below the cold temp when I start it and the temp gauge want go above the Celsius Lin even if I let it run for an hr.the only way the Temp will get to where it needs to be I have to drive It.my truck has some what lost power some time it throws on the lightning bolt light when it does that some times the truck bogs down last weekend was the worst I was being jerked back and for like it was takein it last sip of gas so I put it in neutral and had it floor and the rpms wouldn’t move but it was still running it would revup put in park and floored it and it took so long slowly climing it would not go past 3500rpm and when it did reach 3500 it wasn’t obnoxious sounding. so I.let it sit threw the holiday and no other dash cluster on right now just engine light
    Still says knock sensor that’s it.and it makes a squeak sound like every so often coming from up under the hood it’s not a pulley I’m pretty sure it one of the pulleys wheels . Could that have something to do with the coolant and knock sensor. That’s the only ode I’m reading.can someone please help

    1. I’m actually having the same problems on my Jeep. Red lightning bolt and everything. I’m assuming it’s the EGR VALVE

    2. It’s your transmission causing your torque converter to get too hot which will cause your vehicle to overheat, but also if your temperature gauge don’t move till you start driving then you need to change your thermostat you have a bad thermostat that’s why it’s not showing its overheating

      1. Your torque converter will overheat if the oil pressure gauge fluctuates from high to low at idle

  5. I have a 2005 Ford Escape, great little car. Problem engine light came still ran great, took to repair shop. Needed EGR sensor, replaced. Drove home light came back on, repair shop again, they fooled with it no problem, said it was pulling good reset. Drove home next day drove 6 miles light back on, still running great. Due to go back to shop on Monday now for a EGR valve. Help anyone else haviing or had this problem?

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