[chris335]

delete post

[ctuna]

So you are saying it suddenly got worse?
Or is this a new phone or phone cable?
Changing the cable or the phone would be the first step
to isolate the problem if there is one.
The aux Input is known to be weak or low fidelity.
Which BMW system do you have in the car L7, Hi Fi or stereo?

[mweisdorfer]

I would get the Rockford fosgate Bluetooth adapter. You plug it into the cigarette lighter and Bluetooth your phone to the adapter. The adapter plugs into your aux sound.

The result is you now have a Bluetooth setup in your car. You can even plug in a USB / lightening adapter to it so you can keep your phone charged.

I have one on my logic 7. It sounds way better then the stock analog set up; I have an 07 without idrive and no USB, but I do have the analog plug in to the radio.