Another thing to check...
- After the engine is warmed up and the white smoke has stopped, find a long downhill slope
- put the car in a gear lower than normal so that the engine will brake the car slightly as you come down the hill
- at the bottom of the hill, press the gas pedal while looking out the rear mirror (if you have any trouble with looking out the windsheild at the same time you are looking in the rear-view, then get someone else in the car to look for you)
Try this a few times, and if on acceleration from the coasting you see a cloud of white smoke, this probably means you are due soon for an engine rebuild. I always saw this condition within a few thousand miles of my engine popping.