White smoke or water vapor from the exhaust. You notice white smoke coming from the exhaust when you start your car. If it is cold out, this may be normal. If the smoke does not disappear after the car is warmed, you have a problem.

Transmission fluid may be entering the intake manifold through vacuum modulator.
Replace vacuum modulator
Cylinder head gasket may be bad.
Replace cylinder head gasket.
Cylinder head may be warped or cracked.
Resurface or replace cylinder heads. (Resurfacing is not a DIY job)
The engine block may be cracked.
Replace engine block.