idle+ huge spurts of exhaust gas, 2006 530i
my car, a 2006 530i, has a rough idle problem. When I stop after driving it, let's say at a traffic light, the idle rpm fluctuates between 600 to 700. I can feel a lot of vibrations on the car seat, and the steering wheel. the car seems to be revving up. Also there is a lot of almost whitish smoke coming out in spurts when the car is stopped at a traffic light. it goes away once i start driving it. i looked around quite a few times to see if the other cars were doing this. very few did so but the exhaust gas was clearer and much lesser than mine. This happens even if I have been driving for more than 20 minutes at speeds of 40 miles and above. i took it to the dealer, he says everything is fine. i don't buy that. i live in Maryland. any suggestions?