What does it mean when the exhaust pipe sputters and sprays water at idle?

[VonJohn]

When the exhaust pipe sputters and sprays water at idle, it indicates that the gasoline is burning very well and completely in the engine. The byproducts of complete gasoline combustion are carbon dioxide and water. Due to the high temperature inside the engine, the water is initially expelled as steam. When this steam reaches the cooler tail section of the exhaust pipe and encounters the outside cold air, it condenses into liquid water and flows out of the exhaust pipe. However, if white gas is emitted from the exhaust pipe during summer when outdoor temperatures are high, it is abnormal and indicates that the engine is burning coolant. Idle is an operating condition of a car where the engine runs in neutral gear. The engine speed during idle is called the idle speed, which can be adjusted by modifying the throttle opening size.