Smoke and emissions
Smoke leaves the vehicle from the SILENCER (exhaust). What colour it is tells you what is wrong.
Black smoke means too much fuel is being burned - a dirty air filter or a fuelling fault. Blue smoke means the engine is burning oil, which is wear. White smoke that does not clear means coolant is reaching the combustion chamber.
Smoke is not just an emissions problem; it is the engine reporting a fault that will cost more later. A vehicle that visibly smokes will not pass its pollution test, and it should not be driven until the cause is fixed.