My 94 540i started idling rough when started inthe morning. Replaced plugs with + fours but did not help. Wondering if it's related to my other problem which also started recently and it's a buzzing nose close to the coolant reservoir. It comes on some days and then on other days it's not there. Sounds like a valve of some kind because when I shut the engine it also shuts down at the same time and one can hear it shut down.