I have an 01 Grand Prix GT 3.8L displaying PO141 code, smells like fuel in oil and has used a lot of fuel just testing the car since it's off the road. It won't accelerate beyond 3-4k before dropping back down, dosen't stall though. I can give details on what I've checked but my question is this; Can the O2 sensor (post cat) failure alone create these symptoms? No other codes except there was a misfire on cylinder 3 after really giving it some gas. Too much gas caused by an O2 sensor?