I have never replaced the after-cat O2 Sensor on my '96 XJ and have replaced the front O2 Sensor 2 times over the past several years. I have 225K miles on the XJ and have started getting the P0138 codes again. I thought I'd fixed it before w/out replacing the O2 sensor.
My question/concern mainly is the fuel mileage. My mileage seems to be getting worse by the week. Everything that can effect mileage has been checked, tested or replaced (other than the rear O2 Sensor) and yet my mileage is still around the 13-14mpg (highway & city driving) whereas I have averaged about 18-20mpg (highway & city driving) since I bought this XJ about 6 years back. No mods have been done to the XJ that would effect mileage in that time.
I really don't want to have to drop $60 on a new O2 Sensor if it really has nothing to do w/performance of my XJ. I suppose my Cat could be going bad as that's not been replaced in over 120K miles.... but I don't want to just throw money and parts at the jeep unless it's money well spent.
Any gains to be had from replacing the rear O2 Sensor? Anything like replacing the front O2 Sensor?
Thanks
My question/concern mainly is the fuel mileage. My mileage seems to be getting worse by the week. Everything that can effect mileage has been checked, tested or replaced (other than the rear O2 Sensor) and yet my mileage is still around the 13-14mpg (highway & city driving) whereas I have averaged about 18-20mpg (highway & city driving) since I bought this XJ about 6 years back. No mods have been done to the XJ that would effect mileage in that time.
I really don't want to have to drop $60 on a new O2 Sensor if it really has nothing to do w/performance of my XJ. I suppose my Cat could be going bad as that's not been replaced in over 120K miles.... but I don't want to just throw money and parts at the jeep unless it's money well spent.
Any gains to be had from replacing the rear O2 Sensor? Anything like replacing the front O2 Sensor?
Thanks