Ray, my O2 sensors went two years ago at about 110k. I had the local Nissan mechanic work on it, but I stayed with him while he did the diagnosis. My problem was that the thermostat had failed open, the engine never got above 173 deg F (I think that is it) so the O2 sensor control circuit never kicked in. The car ran on the fixed input curve below 173, thus rich and caused the O2 sensors to carbon up and fail. Replaced the thermostat and O2 sensors and everything settled out. The O2 reading fluctuates a lot when they are working right and the engine is above 173 degrees. My symptoms were that the idle stayed above 1k and the O2 readings never changed. Good luck
06:12:33 05/23/11
