BMW 318Ci e46, automatic transmission. This started happening after the alternator failed and got replaced.
This only occurs when stopping with gear on and rpm drops very low. Absolutely no problems when idling with neutral/parking gear.
First it sound like its about to stall and then rpm starts jumping between 500 and 1000rpm.
Is this related to the alternator failure or did the mechanics screw something up?
EDIT: Voltages are fine according to on-board computer test.