O2 ?

[GUMP]

Originally Posted by Jeff Stout

If a O2 sensor is going bad what will it do? Mine is showing 18 to 21 AFR now and car is fine and runs the same. Last month it was showing 16 to 18 AFR. No header gasket leak that I can hear or see. Plugs read normal and ET is where it should be. The sensor is about 3 years old with C12 and C16 for fuel

Where is the O2 located in the header? I normally change my O2 about once a year or at the first sign of an issue.