Due to the varying climactic changes here in Chicago over the last few weeks I've noticed that during warmer weather (i.e. around 70F) the car idles a little rough. However, when the temp is around 40F, like tonight, the car idles real smooth. I understand that when the temp is low, the air is denser and therefore more air can be packed in the cylinders and when the air is warm (less dense) less air in the cylinders. But does this effect the idle also? Thoughts anyone?

Adrian
1990 535im
1999 K1200RS