The air diverter valve is a part of your air injection system. In practically every modern vehicle, you will find a type of air pump that serves to deliver air to the exhaust stream so that it can be re-burned as part of emissions control. Some vehicles use an air pump check valve, while others use an air diverter valve. They both do the same job, and work in basically the same way. The air diverter valve lets air into the exhaust system, and then closes the system to keep exhaust from escaping.

On a carbureted vehicle, the diverter valve works to prevent backfiring during deceleration. When a carbureted engine decelerates, a great deal of fuel is taken into the exhaust, and if it is not diverted out into the atmosphere, a backfire can occur. Because the air diverter valve is used every time that you drive, it can eventually wear out, and even fail. Usually, it is replaced at the same time as the air pump.

Signs that your air diverter valve needs to be replaced include:

  • Backfiring
  • Sluggish engine
  • Check Engine Light is on
  • Emissions test failed

If your vehicle is displaying emissions problems like those identified above, it could be due to any number of problems, one of which could be the air diverter valve. You should have your emissions system checked out by a qualified mechanic, and if necessary, you should have the air diverter valve replaced.

This article originally appeared on YourMechanic.com as How Long Does an Air Diverter Valve Last? and was authored by Valerie Johnston.


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