Black smoke from the exhaust: What is the problem?!

Black smoke from the exhaust
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Black smoke from the exhaust is a sign that the engine is burning too rich a mixture of fuel and air. A rich mixture is a mixture that contains less air than is necessary for the complete combustion of the fuel.

This means that a larger amount of fuel enters the cylinders than would belong to a certain ratio of air, due to which incomplete combustion occurs. This incomplete combustion results in black smoke from the exhaust, which contains a large amount of soot.


Burning a rich mixture, accompanied by black smoke from the exhaust, may be due to a malfunction in the fuel system or a problem with the air supply.

Several components can cause black smoke from the exhaust, though this differs per engine type:

  1. Petrol engine
  2. Diesel engine

1. In the case of a petrol engine

2. For diesel engine

  • High-pressure fuel pump failure
  • Air weight failure
  • Injector failure

With both of these engines, the combustion of a rich mixture can also be caused by an excessively clogged air filter. However, the combustion of a rich mixture does not have to be manifested only by increased smoke.

Among other things, black smoke from the exhaust can be accompanied by high fuel consumption, difficult starts, or loss of power.

The good news is that in the short term, burning a rich mixture cannot significantly harm the engine. Though, in the long run, burning a rich mixture can lead to serious malfunctions or problems, which is why you should solve this problem as soon as possible and not waste time.

An engine that burns a rich mixture produces black smoke from the exhaust and more soot.

This soot gets into the engine oil, which leads to faster carbonization of the piston rings, clogging of the oil filter, or lubrication channels through which the engine oil is guided. The result is degraded engine oil and insufficient lubrication, which leads to greater wear and tear of individual engine parts.


Therefore, as many may think, black smoke from the exhaust is not just a syndrome of improper exhaust manifold modifications. This color of smoke can appear in any car that burns a rich mixture.