What are the different types of engine smoke: Types of car smoke and what they indicate


We know that the human body shows many symptoms when a disease occurs and doctors can make a preliminary diagnosis based on these symptoms. 

Similarly, when any component of an engine becomes compliant, it shows its own set of indications, and it gives a rough idea of ​​the problem of the engine.

The indications shown by the engine can sometimes be in the form of an engine warning light, sometimes through an abnormal noise, or even through engine exhaust smoke.

Here we can learn about the different types of smoke emitted from a vehicle and the engine problems that each of them indicates.


 Types of smokes emitted from an engine

For an ic engine, it works by using the energy produced by the burning of fuel, the end product that comes after this is mainly emitted in the form of gas.


The colour variations of the exhaust gas/exhaust smoke emitted in this way often indicate some problems in the engine.


These are  the different types of smoke  emitted from a vehicle,
  • Black smoke
  • Blue smoke
  • White smoke

Reasons behind black smoke emitted from the engine 

Atmospheric air is essential for any object to burn completely. Similarly, in the case of vehicles, the right amount of air is required to burn the fuel completely.

Thus, when the right amount of air is not available, the engine emits black smoke.

But having the right amount of air does not mean that the fuel will burn completely. For this, the air-fuel must be properly mixed and burned at the pressure and temperature required for the fuel to burn completely.

From this, it can be seen that these three main factors influence the production of engine black smoke.

  • The Rich amount of fuel or lean amount of air
  • An improper mixture of air and fuel
  • Defects in engine timing

As mentioned above, the main cause of black smoke coming from a vehicle is an increase in the amount of fuel in the engine rather than air.

What could be the reasons for the increase in fuel level in the engine or the decrease in air volume?

Let us first look at the causes of air depletion in the engine, 

The first thing to pay attention to when checking the air intake to the engine is the air filter. If the air filter is too dirty it will adversely affect the amount of air entering the engine.

The second thing to check is the turbocharger, 

We know that the function of a turbocharger is to pump the required amount of air into the engine. Therefore, if the performance of the turbocharger decreases for any reason, the amount of air entering the engine also decreases.

In such cases, the engine does not get enough air and as a result, the engine emits black smoke.

These are the two main reasons for the decrease in the amount of air coming into the engine.

Now suppose the engine is getting the right amount of air but if for any reason the amount of fuel increases it will cause the engine to emit black smoke.

So let's see what are the reasons for getting more fuel in the engine.

We know that in older petrol vehicles the fuel was supplied by carburettors, So problems with carburettors can cause black smoke to come out of vehicles.

In the case of diesel vehicles, fuel injectors supply fuel to the engine, But the fuel pumps determine the amount of fuel coming into it. Therefore, malfunctions of the fuel pump cause black smoke to come out of the engine.

However, in electronic fuel injection vehicles, the amount of fuel and the time of injection is controlled by the ECU. ECU determines this based on the data received from the engine management sensors. After understanding the engine load, speed,  temperature and the amount of air entering the engine, ECU determines it. Such data is provided to ECU by engine management sensors.

Failure of the ECU or faults in the engine management sensors may affect the amount of fuel to be injected into the engine. This causes black smoke to be emitted from electronic fuel injection vehicles.

Also, fuel injection vehicles have a fuel return pipe and a fuel regulating valve. It is used to maintain constant pressure in fuel pipes and fuel rails.

If this fuel return pipe becomes blocked or the fuel regulating valve does not work properly, the ECU may receive incorrect information and increase the amount of fuel injected. This causes black smoke to come out of the engine.

As mentioned above, if the air and fuel are not mixed well, black smoke will come out of the vehicle. In older petrol vehicles, the carburettor nozzle was used to mix air and fuel.  In fuel injection vehicles this is done by injectors.

Injectors spray fuel at high pressure into the air entering the engine cylinder,  which is known as atomization of fuel.

If any of the atomizing nozzles in these injectors become blocked or the injection pressure drops, it will cause black smoke to come out of the engine.

The engine's miss timing is another reason for the black smoke coming out of the engine.

But this can sometimes be seen in vehicles that have no problem with engine timing. This can sometimes be due to any valve leak, In such cases, the pressure inside the engine cylinder decreases and the fuel does not burn completely.

Black smoke can sometimes come from vehicles that do not have any of the problems mentioned above.

This can happen if the engine does not overhaul on time. Under these conditions, there may be a lot of carbon deposits inside the engine, which burns and emits black smoke from the engine.

These are the main reasons for black smoke coming from the engine.


Reasons for blue smoke emitted from the engine

Blue smoke is another type of smoke that is likely to come out of the engine. This is usually caused by the burning of engine oil inside the engine, which can lead to a decrease in engine oil level and sometimes engine cease.

Check the engine oil level when such smoke comes out, and if there is a significant drop in the oil level, it can be assumed that the engine oil is burning.

If there is a trace of oil in the exhaust pipe or the smell of oil in the exhaust fumes, it is definitely due to oil burning inside the engine.

If you use the vehicle for too long in this condition, the lubrication will not work properly and the engine will break down.

Circumstances that cause engine oil to burn


The fuel in the engine burns inside the combustion chamber and produces energy as a result. The combustion chamber is situated between the cylinder head and the crankcase. engine oil is present in the cylinder head and the crankcase.

Some seals prevent engine oil from entering the combustion chamber from the cylinder head. Seals can be in the form of valve stem seals, O-rings or valve guides.

Any damage to these seals will cause engine oil to flow from the cylinder head to the combustion chamber and burn there. This causes bluish smoke to come out of the engine.

The piston rings prevent the oil in the crankcase from going into the combustion space and the high-pressure gas in the combustion space from going into the crankcase. That is, the piston rings separate the combustion space from the crankcase.

If the condition of the piston rings is bad, high-pressure gas from the ignition area will leak through the piston ring and reach the crankcase, this is called piston blow-by.

When a piston blow-by occurs, the pressure in the crankcase increases, causing damage to the O-rings and seals in the crankcase. This causes the oil inside the crankcase to leak out.

Even if piston blow-by occurs, it needs to be ventilated to prevent pressure build-up in the crankcase. In the past, an air pipe was used for this purpose. The government banned it, finding that it emits oil vapour, which can cause air pollution.

So this pipe is connected to the air inlet. So that the air containing this oil vapour enters the engine and as a result of combustion it is released as gases that are not more harmful to nature.

This vapour circulation can only take place if the pressure in the crankcase rises for any reason. For this here uses a valve called a positive crankcase ventilating valve (PCV).

If there is any damage to this valve, this oil vapour circulation is likely to occur even if there is not much pressure difference in the crankcase. This causes blue smoke to come out of the engine.

Damage to the turbocharger may be the next cause of oil burning in the engine. The oil reaches the turbocharger for lubrication, Therefore, if the oil seal used in the turbocharger is damaged, there is a risk of oil entering the engine. This causes blue smoke to come out of the engine.

Reasons for White smoke emitted from an engine


White smoke is another type of smoke that is likely to come out of the engine. This is the steam that forms when the coolant burns inside the engine, It comes out of vehicles in the form of white smoke.

The coolant enters the combustion chamber when the cylinder head gasket fails or the cylinder block cracks. The coolant that enters in this way burns and comes out as white smoke.

The coolant that enters the engine sometimes enters the crankcase and mixes with engine oil to form a white, thick liquid.

If such a liquid is found in the engine oil cap, it means that the coolant is burning inside the engine. A significant decrease in the coolant level and a change in the colour of the coolant are symptoms of coolant burning inside the engine.

Regardless of this, if the vehicle is driven for long distances, the coolant will run out completely and it will cause the engine to overheat.

These are the various types of smoke that usually come out of vehicles. If you notice this type of smoke coming from your vehicle, confirm the problem with the help of a mechanic, it will enhance the life and future performance of your vehicle.
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