My old ecu told me my heater sensor was bad on my 02 sensor back in the summmer. The car ran great and everything was fine until it got cold. My car stutters and falls on its face around 2500 to 3500 rpms untile the car is warmed up, about 3-4 blocks of city driving. I think the 02 sensor is causing this to happen.

If I shut the car off for 5-6 min and drive again, it will buck for a few more blocks then go away. plus my a/f gauge is reading funky.

 

its not the o2 sensor because you can unplug it from the harness and your car should still run perfect just a little rich. But it hesitates thats another problem.

 

can anyone else clarify why it does it when its cold and then goes away

 

it was the 02 sensor! car runs great