you mean the car Ҽxhaust?
if your car is petrol and using a carburetor...means maybe the auto choke let in too much fuel into the engine....
Black smoke indicates a rich fuel mixture.
Black smoke from a petrol engine is primarily caused by an overly rich fuel mixture, where too much fuel is being burned compared to the amount of air. This can result from a malfunctioning fuel injector, a clogged air filter, or issues with the engine’s sensors, such as the mass air flow sensor. Inadequate combustion due to poor ignition timing or faulty spark plugs can also contribute to the problem. When unburned fuel exits the exhaust, it creates the characteristic black smoke.
if it is white smoke engine need to rebuilt.
Exhaust should be colorless and odorless.
nothing the 2stroke-petrol will smoke as it burns the oil which should be mixed in it
Black smoke = excessive fuel entering the engine
Black smoke from an engine is caused by unburnt fuel.
The black smoke that a diesel engine blows out is fuel that is unburned. The black smoke can be caused from over-fueling, poor fuel quality, or dirty or worn fuel injectors.
Service engine
The color of the smoke will help identify the problem. Blue smoke is engine or transmission oil. Black smoke, excess fuel. White smoke, engine coolant.
In a diesel engine, blue smoke is an indication of oil being burned. Black smoke means that there is incomplete combustion of the fuel. White smoke can be seen when raw diesel fuel is not being burned.