If the engine is warm and the smoke coming out of the vehicle's exhaust is white, which of the following is the most likely cause?

Correct answer: Water entering the combustion or explosion chamber.

With the engine already warm, white smoke that does not go away can indicate water or coolant entering the combustion chamber, often because the head gasket is damaged. When starting a cold engine, a little white smoke is water vapor and soon disappears. Excess fuel and a dirty air filter produce black smoke. In the image, white smoke comes out of the exhaust of a motorcycle with its engine running.

Why is white smoke coming from my car exhaust? · Mecánica y entretenimiento simple del automóvil