[Taxvictim]

Last week my 6th cylinder started misfiring. Did all the tests of swapping the ignition coil among cylinders to identify it as the problem, then replaced it with a new one from Advance Auto. Not OEM. Everything worked great.

One week later, I'm getting a misfire again. Figured it for another ignition coil since the car is getting so high in miles. Local stores did not have them in stock, so I bought TWO from the BMW dealer. Bosch OEM.

Went home and opened her up, changed all the plugs while it was open, and replaced the ignition coil in the problem cylinder plus decided to put a new one into another cylinder anyway. Upon restarting, both of the new OEM cylinders were misfiring. Did all the tests of swapping them out, etc., and they would not work in any cylinder. Put the old ones back in, and the car ran normally (even with the supposed coil that was not working earlier).

I checked online to make sure the dealer gave me the right parts, and every part supplier says this part number is for the E90. Any ideas as to why this would happen? Car has 90k miles.