Sometimes my truck will start running rough, it doesn't seem to matter if its cold or hot, idling or driving. Something I've noticed monitoring my STFT, when its running good both banks are around 0.90 - 1.10 . when it starts running rough bank 1 drops down to 0.64 and stays there, like its a minimum value , while bank 2 stays around 1.00 and seems to be adjusting normally. then all of a sudden its like a switch is flipped and bank 1 jumps back up to around 1.00 and it runs smooth. I swapped bank 1 and 2 cops but the problem stays on bank 1. The O2 sensors are about 1 year old. Could a wire be shorted or broken? Any ideas? Thanks in advance.

 

Your STFT values are by no means bad or extreme. And by no means minimum or maximum - which would be down around negative 25% or up over positive 25%.


Some more details would not only be helpful, they are mandatory if anyone is able to help.


Engine type, mileage, maintenance history, any codes, other symptoms, noises? Does rough idle disappear if you rev the engine and return to idle? What kind of reader you using?