Rattle Rear Passenger Door 2008 E90 M3

[InnerBlueSkies]

Did a search (didn't see much on this particular forum), thought I'd post my experiences as inevitably some of you may encounter this problem as our cars age.

Going over rough roads, I've been encountering a consistent, at times unbearable rattle, almost similar to the exhaust rattle some of our cars give off at times.

I recently swapped out the window regulator (an unfortunate coincidence in this story) and that is when the sound started. To troubleshoot (and this is the interesting part).

I removed the door card and no rattle. Swapped out clips, reassembled, and same rattle reappeared. Renewed seals on door with Gummy Phledge, Same rattle, Isolated doors lock pin, same rattle.

I basically gave up, as many of you know, there are only so many times you can disassemble and reassemble parts on a 12 year old car without snapping clips and making the situation even worse.

Turns out the sound is coming from the center console rear cup holder. The acoustics of the car with the door card in place will fool you into thinking it's coming the door. I even had passengers sit back there while I drove and identified it as the source of the rattle. If you are experiencing this rattle, manipulate the cup holder and rule that out before wasting your time doing all the steps I did.