Cars emit black smoke: Causes and solutions

Many car users often do not care about the car emitting black smoke because they think it is because the engine burns excess gasoline. But this phenomenon continued to persist and the amount of black smoke emitted was increasing, the engine was operating poorly… then the car was brought to the garage. By then it was too late. Let’s find out the causes of “black smoke” in cars and find ways to fix and handle them with CarOn!

What causes the car to emit black smoke?

Engine air filter clogged

The reason the car produces black smoke may be because the car’s engine air filter is clogged with dirt, and the engine lacks oxygen to catalyze the fuel combustion process in the combustion chamber. This leads to a situation where the fuel is not completely burned, and the exhaust gas is released creating black smoke.

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To fix this situation, car owners need to check the engine air filter. If there is a lot of dirt causing blockages and hindering the air filtration process, you need to clean the air filter as soon as possible. According to the manufacturer’s recommendations, car air filters need to be cleaned every 5,000 km and replaced every 20,000 km. Depending on driving conditions, car owners can clean the air filter sooner. In case the engine air filter is torn or moldy, you should replace it with a new one.

Spark plugs cling to soot

If the engine air filter is not cleaned or replaced for a long time, it will accumulate soot and form dirt. When the spark plug ignites, black smoke is produced. In this case, you just need to regularly check and clean the air filter, and replace the spark plug, helping the ignition operate smoothly. This has just been fixed The phenomenon of the car emitting black smokeand helps the car’s ignition work better.

Learn more about car spark plugs through the article below:

Poor quality fuel

If you unfortunately use dirty fuel, mixed with impurities, etc., the combustion process will not be highly effective. This leads to unburned fuel in the engine combustion chamber and is discharged through the exhaust pipe, creating black smoke. In addition, if the vehicle regularly uses poor quality fuel, it will also encounter other problems such as uneven engine start, vehicle jerking when stepping on the accelerator, engine overheating or even sudden stalling while moving. .

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Normally, fuel that is dirty or mixed with impurities is difficult to detect with the naked eye. Therefore, if the car has one of the above signs, it is necessary to take the car to a repair and maintenance center for inspection and have all the poor quality fuel inside removed. Then clean both the fuel injectors, fuel injection pump and cylinder combustion chamber to remove all remaining dirty fuel.

Damaged fuel filter

When the fuel filter is clogged, the amount of fuel pumped into the combustion chamber is not enough, causing the air mixture to decrease effectively. Fuel burns prematurely or late causing incomplete combustion, causing the vehicle to emit black smoke. In addition, a clogged fuel filter also causes loud engine noise, wastes a lot of fuel, and makes the car difficult to start.

Fuel filter clogged with caron

To overcome this cause, you need to regularly clean to remove dirt and replace the fuel filter every 40,000km according to the manufacturer’s recommendations.

Clogged fuel injectors

After a long time of use, fuel injectors often become dirty and soot, leading to injector blockage. When the injector is clogged, the amount of fuel entering the combustion chamber is reduced, reducing combustion efficiency and causing the car to emit black smoke.


If the problem lies in the fuel injectors, the injectors need to be checked and cleaned. According to recommendations from experts and automobile manufacturers, injectors should be cleaned every 15,000 – 20,000 km of operation. Depending on operating conditions, car owners can clean sooner or replace new injectors, helping the car operate smoothly and save fuel.

High pressure pump malfunction


When the fuel pump/high pressure pump is clogged, it will weaken the pressure, not ensuring the necessary amount of fuel for the engine combustion chamber, the fuel will not mix well with the air and will not burn completely, creating large amount of black exhaust gas. This is also a common cause of black smoke from the machine.

After a long period of use, the fuel pump may malfunction due to dirt, wear, or frequent overloading. However, in reality, the car fuel pump system is quite durable, so if inspection shows serious problems, it needs to be replaced. In addition, when cleaning the high pressure pump, it is necessary to completely clean or replace the fuel filter and injectors.

Engine piston is worn, air pressure is poor

pston is worn out

The function of piston rings is to prevent engine oil from penetrating inside the combustion chamber. However, during operation, the piston ring is corroded by combustion gases, lubricating oil and friction with the cylinder during work. When the Piston wears out, engine oil begins to flow into the combustion chamber. The process of burning this mixture produces black smoke.

This is one of the serious failures because damaged pistons can cause the engine to stop working. Therefore, when you encounter engine piston errors, you need to take your vehicle to a reputable vehicle maintenance center.

In case the car emits black smoke, it is not a cause for concern

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Diesel engine cars such as Toyota Fortuner, Ford Everest, Hyundai SantaFe… after many years of use, it sometimes emits black smoke when starting the car. This is a normal phenomenon. Because in the early stages of starting, the incoming air is not enough, causing excess fuel to burn, causing the car to emit black smoke. But after just a few seconds when the engine works stably, the black smoke will no longer exist. This is a normal phenomenon, nothing to worry about.

However, if the vehicle continues to emit black smoke while moving, it is certain that the operating system has malfunctioned, so you should proactively check it as soon as possible.

How to fix a car that starts emitting black smoke

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When black smoke appears from the car’s exhaust, the car owner should check the car’s parts and fix this situation soon to ensure safety and minimize future repair costs. Some ways to fix a car that starts emitting black smoke:

  • Periodically clean and replace the engine air filter when you see black smoke from your car.
  • When the spark plug is covered with dust or dirt, you should check it and replace it with a new one if necessary.
  • Clean the car fuel filter periodically or replace the fuel filter with a new one if the vehicle is used more than 40,000km.
  • Replace new injectors or clean injectors periodically, this helps the vehicle’s combustion chamber engine to be better protected and save fuel.
  • Replace the high-pressure pump and clean the fuel filter to help the vehicle operate better and limit black smoke.
  • A pressure gauge in the combustion chamber can be used to determine damaged parts.

To keep the vehicle running in the best condition, vehicle owners should bring the vehicle to reputable maintenance centers for inspection and repair. Regular maintenance checks will help the vehicle operate smoother, more optimally and limit many potential risks.

Where is reputable car maintenance?

Cars emitting black smoke is not a rare phenomenon, but this situation cannot be prolonged, it will affect the vehicle’s performance. Therefore, you should check your car regularly and have a regular maintenance plan, early detect problems and causes of black smoke from your car for timely handling.

We would like to introduce a trusted brand used in the “car maintenance” market – CarOn Pro. A team of experienced technicians, dedicated consultants, quality products – these are the things that CarOn always preserves and develops to bring customers the best quality service experiences. . Coming to CarOn, your beloved car can rest assured on the long road, let CarOn take care of everything else!

For further information, please contact hotline 0961.247.360 or website for the fastest consulting support.

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