My car has been getting less than 20 miles per gallon. I recently got a code for the front 02 sensor after I replaced my fuel pump and cleaned my throttle body but then it went away on its own. However, the car sure seems like the 02 sensor might be causing problems.

What other symptoms might tell me that the 02 sensor needs to be replaced besides bad gas mileage? If I have no CEL or code for it, do I always assume that it does not need to be replaced?

By the way, I've already changed the knock sensor, got new tires, a new radiator, tranny fluid and oil change and am running 91 Octane with a bottle of Chevron Techron. I'm about to change my PVC valve and spark plugs (NGK coppers).

Any advice would be appreciated. Thanks.

 

I've done everything you've said, and no gains. Hope you have better luck than me.
Jae

 

....and we're both in SoCal where the "winters" don't generally drop below 40 degrees. This doesn't make sense.

I'm confident that if I brought my car back east (where I'm originally from) it would committ suicide before making it through one winter.