I have a 95 f-150 xlt w/5.0 liter

The engine was hesitant on acceleration, rough idle, poor mileage and engine light would come on.

I checked the codes and they came back with an oxygen sensor problem.

I replaced the oxygen sensor. Everything was great. Mileage came back to normal, ran like a champ. Lasted about 10 days. The symptoms re-appeared.

I replaced the oxygen sensor again, figuring that I bought a bad one. It cleared up the symptoms for about 7 days. The problems are back.

I figure something is causing the oxygen sensor to fail. Any ideas?

 

have you recently done any engine work and used old style rtv or silicone sealer. big problem when O2 sensors first came out. shortly after engine repairs the O2 would crap out. the early rtvs were contaminating the sensors. must always use low volatility rtv.

a remote possibility is a head gasket leak where the sensor is getting contaminated by antifreeze.