I am new in this forum. I bought a 2002 320i BMW with 200K on it last month. After few days I realized that the car was shaking when I started it off and the light engine came on. I showed it to our local BMW. They found a misfire on cylinder # 6 along with a fault on the mass airflow sensor. They changed the coil on cylinder #6. After one day, it happened again. I showed it to another mechanics (BMW Specialists!) and he changed all six spark plugs but the problem did not go away. I have spent about $700 so far and I do not really want to spend more (I would buy a new one if I wanted to spend more!). It usually happens in idle condition when the rpm comes down from 1200 to 600 and when I just start the car in the morning. If I turn off the car or when the car gets warm, the problem usually goes away. I also found that if I push the accelerator for about 1-2 minutes, it does not shake. The light engine comes on and off intermittently. Moreover, I feel sometimes hesitation in low gears. One of my friends suggested me to shift from premium to mid-grade gas. I might try that nest time. All your comments and helps are greatly appreciated.