i am workin on fixing my friends car i thought i knew what was wrong but now i am so confused. i was planning to take out one of his O2 sensors and take a look @ it and try and clean it alittle. the O2 was black so i figure oh the motor is running to rich on that side. but then i pull the number 2 cylinder spark plug and the tip is shinny like when i cleaned it last week. so then i think the motor is running lean. but then i look @ the tail pipe and there is black soot coming out of that one side when he revs it up.

is it too lean or to rich?? will replacing that O2 fix the problem.

he also gets a random misfire error and a bank 2 shifted lean error