idling problems/misfire sound !please help
i have a 98 bmw 328i have just recently been having problems with. i was getting onto the turnpike not going to lie i had it WOT got up to speed shifted to 5th cruised everything seemed fine until i got off the exit and the car started idling erratically and was making a choppy sound or misfire sound to about 3k rpm then above that seems to be fine. Anyway i began to try to diagnose the problem took it home did a compression test to see and everything seemed to be fine there. then i move on to getting hooked onto a dtc scanner no misfire code only code was o2 sensor bank 2. didnt think that o2 would be the cause of this problem i proceeded and checked all my plugs which were only about 2months old everything seemed fine. then i proceeded to look for a vacum leak ended up taking the intake manifold of to check them all no signs of a leak anywere. fuel filters new the air filters new could this be a rod bearing?? but its not really a loud knocking sound more like a cammed subaru boxter engine sound lol til 3k if you know what i mean. anyone know?