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.

When does an EGR valve need to be replaced?

Symptoms of a malfunctioning EGR valve include:

  • Check Engine Light is on
  • 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 from the EGR valve.
  5. Remove the bolts that hold the EGR valve to the cylinder head.
  6. Remove the EGR valve. Be careful to protect the open cylinder head from any debris.
  7. Bolt on the new EGR valve and attach the vacuum line.
  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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Comments 2


October 19, 2018

Thanks a lot for this information


November 8, 2018

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