My 2002 c240 keeps stalling when I try to brake to stop at traffic. Engine shakes and idling speed goes down to the point that i have to restart the engine. Sometimes the engine does not stall but just goes back to the regular idling speed.i noticed the drop also when the aircon/ heater automatically cranks up. Had it checked at a local shop that repairs Mercedes. Computer did not show fail codes and the battery was just replaced since it was 5 years already. Serviceman said that it is not the alternator since it is charging well. I saw in one forum response that it might be the Mass air Flow sensor and to just replace it. Another said it mught be the oxygen sensor. I need help in figuring this out. Thanks in advance.