White smoke can be transmission fluid being sucked into the intake through a faulty vacuum modulator on the transmission and ignited in the cylinders and out the exhaust ,OR as suggested by member 86560SEL ,steam from a blown head gasket .. with the engine warm, hold your hand behind the ehaust pipe while idling , if water droplets form on your hand ,you probably have a blown head gasket ,if transmission fluid forms on your hand and you can smell the transmission fluid then the modulator is faulty ,check the coolant , if oil droplets are present in there then that's another way to tell if the head gasket it blown ,also check the level of the transmission fluid.

Ben