BMW Repair: Does cold weather cause cylinder misfire?, weather cause, check engine soon light

Question
Have a '02 325i automatic sedan. It has happened twice so far that the car shakes with unstable idle speed, like it's going to stall, when being first turned on in the cold morning. It's over due about 1k miles for the major maintenance. BTW, the spark plugs are new, and the problem happened once one week before the new plugs, and once about 5 days after the new plugs. When it happened the second time, the "check engine soon" light came on. I used my Peake R5 and got 3 cylinder misfire message. So the question is "does cold weather cause cylinder misfire, or the spark plugs that I put in myself did not work right?" If I go to mechanic, what should I tell him? Thanks in advance.

Answer
Jian, Assuming you put the correct plugs at the correct 30Nm torque then no cold weather doesn't cause misfires. Cold season gasoline of poor quality or with too high of alcohol content will cause poor driveability. Take a gas sample to the dealer service department and have them check for alcohol content. Make sure you are using 91 octane or higher from a reputable supplier. If you go to a mechanic tell him that you recently installed plugs. Your misfire maybe totally unrelated to fuel. Just an idea.
-Evan