Remove the carbon from your car

Char by the exhaust pipe of the car

If we have a diesel car, it can pass that in strong accelerations we see how a black and dense smoke comes out of the exhaust pipe . This is nothing but char which can cost us even a rejection in the Technical Inspection of Vehicles.

But, what is the reason why our car expels black smoke? The explanation is very simple: the mixture of fuel and air is not done correctly, causing part of the fuel not to burn well and escape through the exhaust in the form of soot. However, this incorrect air/fuel mixture may be due to several engine problems . Then we will explain what they are, how to avoid them and what needs to be done to fix them.

What causes the char

Causes of the car's carbon

As we have said, it is due to a incorrect mixture of air and fuel , but that can happen three different ways . More air than fuel, more fuel than air or having the right proportion, but badly mixed. The case that there is too much air should not worry you, because the smoke would go white. It is only the other two that can cause black smoke. These are possible causes :

More fuel than air

  • Operation normal diesel engine : do not worry if black smoke comes out when you accelerate at low turns or when you start the car. The normal thing in diesel engines is that they generate some char with normal operation. Especially the old ones. Worry only if black smoke per system, because the problem may be another.
  • Flow meter broken : The flowmeter, MAF sensor or airflow sensor is responsible for > measure the amount of air that enters the engine. Thanks to this, the system can measure well the proportion of fuel and air necessary to make a good combustion. If the flow meter thinks it is entering more air than actually enters , it can cause black smoke. In these cases it is normal to turn on the motor failure warning light on the car's instrumentation. Except if it is an especially old vehicle. It would also be normal to notice a slight loss of power. Changing the flowmeter is usually easy and cheap . There are hundreds of videos like the one below that explain how to change it yourself depending on the model:
  • Very dirty air filter : an air filter so dirty that does not let in enough air can also be the cause of black smoke. The solution is very simple. Take a look at the article How to check an air filter, because it is a very simple process. Anyone can replace or fix it, even if they have no mechanical knowledge.
  • EGR valve damaged : this was a very common problem in diesel with some antiquity. Especially if you did many kilometers in the city or drove at low turns for a long time. As we have told you, the soot from which the black smoke is formed is the badly burned fuel. Well, the EGR valve solves that problem by putting part of that smoke back into the engine, to finish burning well .Unfortunately, this fault is harder to fix and more expensive than the previous two. So you'll probably have to take it to a workshop, unless you have more advanced mechanical knowledge.
Car charcoal

Blend of fuel and poorly made air

  • Dirty injectors
    • Dirty injectors strong>: when the car injectors do not spray well the diesel fuel , the mixture together with the air is not made homogeneously inside the combustion chamber. This will cause areas of high fuel with little air and vice versa. The remedy is very simple, except in particularly serious obstructions. Simply apply a nozzle cleaner or a pre-ITV treatment fluid.
    • Fatigue of mechanical injectors : injectors of direct injection systems (common-rail or pump injector) are piezoelectric, so they do not have fatigue. However, the systems of indirect injection (older but still in circulation), carry mechanical injectors . In some cases it can happen that the needle does not close well the fuel exit hole. This causes droplets to fall to the cylinder when it should not and the mixture decomposes. The result is increased fuel consumption, worse mixing and black smoke.
    • Problem with the fuel pump or the common rail : this is very uncommon, but it may happen that more fuel is injected due to a more serious internal problem. Either a pump-injector system or one of common rail . In these cases you should turn on a witness in the instrumentation of the car and should enter emergency mode . It is fortunate that it is rare, because its repair can be very expensive

    How to prevent excess char

    If your engine has no problems, but generates char as any diesel with a certain age, you can still minimize its appearance . You will only have to acquire some healthy habits for the engine . The normal thing here is to listen to tips like not speeding too much at low turns. And although this warning is not wrong, it is somewhat inaccurate. The best you can do is drive whenever you can within the regime in which the car gives its maximum torque . A range of revolutions indicated by the manufacturer.

    For example : a Seat Toledo II 1.9 TDI 110 HP delivers maximum torque from 1,900 rpm to 2,750 rpm. So the ideal is to take it whenever you can between those two values. Interval in which the engine gets explosions of better quality.

    How to remove the char

     Revolutionize car to remove carbon

    To be able to clean and remove carbon from our car engine, we can continue a series of tips that will help us a lot to reduce the black smoke expelled by the exhaust pipe.

    First of all it is advisable to circulate a while in a normal way so that the engine arrives to its optimal state of operation. Then you have to revolutionize it to about 3,000 or 3,500 rpm , so that the exhaust gases come out with enough force to clean the inside of the char. For this the best thing is to drive around the autoví a for about five or ten minutes. At that speed enough air will enter the radiator so that we do not give an unnecessary heater to go so high in revolutions.In addition, we will also notice that the fuel consumption will be lower, something that will surely appreciate our pocket.

    If you are interested in everything related to the car smoke , do not miss the articles:

    • The smoke of our car
    • Gas Test and Opacity in ITV (Part II)
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