Well guys i cant figuer this out my bronco runs like crap engine shaking and driving ability sucks like there is a miss/stumble but one i unplug the o2 sensor it has more power and the motor smooths out could it be acting up from a faulty injector not wanting to run correctly in closed loop??? The only code im getting is 311 ive check all valves and piping and cant find anything any help would be much appericated thank you

 

what year, motor? any mods to exhaust? have you checked fuel pressure at the rail with a gauge? have you correctly checked your timing and what is it at? any exhaust or vacuum leaks?