Hi , my first post and question. My e24 rough idles after its warmed up and been driven. eg at traffic lights the car almost stalls. The idle ramps up and down, and then stalls eventually. There is also a mechanical whirring noise from the engine which occurs at the same time. I think ive narrowed it down, my take is the bearing in the alternator is slowly seizing up, and putting load on the engine? i tested it by taking of the alternator / water pump belt and the whirring stopped, and the idle was fine again. So would a problem with the alternator (most likely not water pump?) cause this rough idle and stalling?