What Causes Carbon Buildup on Pistons?

April 23, 2022

Carbon deposit buildup on pistons and piston rings.

Many drivers would not want the outside of their engine to look dirty. Yet it doesn’t matter if the outside of your engine looks a bit messy. The important thing is that the inside of your car engine is clean. If there are carbon deposits inside your engine pistons, the performance of your car engine might get affected. Of course, the carbon buildup has many possible causes. It might be due to the wearing of engine parts due to prolonged usage of your car. It might also be due to poor fuel or oil quality. 

So, if you are meticulous in taking care of your car, it will be best to check for carbon buildups regularly. In this way, you can prevent the onset of more serious issues in your vehicle due to carbon buildup. It will be helpful to bear in mind that carbon buildup in the pistons and other parts of your engine is one of the primary reasons the engine eventually fails. Hence, you should always be wary of the symptoms of this problem.

Understanding Carbon Buildup

Carbon buildup refers to the carbon deposit or accumulation due to incomplete combustion. It happens when the piston rings don’t seal off or close well the combustion chamber. Carbon buildups usually beset many newer vehicles that feature direct injection systems.

Your car’s engine burns fuel and releases waste products, which eventually get deposited in the intake manifold, DPE oxygen sensor, EGR, and many other engine parts. If you don’t have these deposits cleaned, they build up over time and cause many other engine problems.

Major Causes of Carbon Deposits on Piston?

As mentioned above, there might be several causes of carbon deposits. As a car owner, it will help to know the possible causes of these carbon deposits so that you can avoid them or prevent them from becoming the cause of your engine failure: Below is a rundown of these possible causes:

Use of Substandard Fuel

First, it could be due to substandard fuel quality. Substandard fuel would not sufficiently burn in the engine. This inability to burn completely will create carbon deposits on the piston ring groove, combustion chamber, intake valve back, and sparkplug.

Bad Driving Habits

Another possible cause of these carbon deposits is terrible driving habits. Your driving habits, of course, can contribute to the buildup of carbon deposits in your engine. For example, if you often run your car engine at maximum speed, you cause your throttle to be wide open, called WOT or Wide-Open Throttle

The RPM range is the WOT rating or the range the motor must achieve when you set the throttle at its maximum. As a driver, you should be wary of the RPM range and ensure that you operate the engine within the recommended RPM range.

WOT tends to make the engine sufficiently hot to burn away contaminants that could become deposits. If your car engine is idling around more often, you promote the onset of carbon buildup.

Worn Piston Rings

When piston rings get worn, it becomes easy for oil-based carbon to build up. Oil, likewise, leaks beyond the rings. It can also leak out from valves onto the combustion chamber. Oil-based deposits might appear dark black and gummy. They got that tar-like consistency that is sticky. 

Carbon deposits tend to cover or coat surfaces that get exposed to the combustion process or those components that deal with the engine exhaust. These deposits can also form on spark plugs, throttle bodies, and intake manifolds. 

On the other hand, if you got an excessive mixture of air and fuel, carbon build-up might also occur. Besides, if there’s too much fuel, it might lead to large carbon waste that is difficult to remove.

Faulty Computer

The buildup of fuel-based deposits might be due to a faulty computer. It might be that the computer is not giving the proper signals, causing excessive fuel amount to get burned in the combustion chamber. 

Pushing the Throttle Too Much

As mentioned above, bad driving habits are one reason why carbon buildup happens. Suppose you are an impetuous type of driver. You might slam on the engine throttle while you drive. If you do this, the car will overfill. If the fuel doesn’t get burned entirely, carbon deposits may ensue.

High Gear Speed

If you’re driving a manual transmission car, you might experience failing to shift gear while driving. For example, you might be at a low speed while driving at high speed. The engine, of course, will necessitate more supply of fuel once you go for the high speed. 

But if you keep the gear at high speed even if you are driving slow, you might over-pump gasoline onto the engine, and the car engine would surely fail to burn the pumped fuel entirely. Thus, carbon buildup occurs.. 

But if you keep the gear at high speed even if you are driving slow, you might over-pump gasoline onto the engine, and the engine would surely fail to burn the pumped fuel entirely. Thus, carbon buildup occurs.

What is the Impact of Carbon Deposits on an Engine?

The buildup of carbon is an ordinary aspect of the combustion process. So, if you run the engine, you will most likely get a few carbon deposits in some parts of the car engine. However, if there is too much buildup of carbon deposits, these deposits might affect the performance of your car engine. 

If you don’t address these carbon deposit issues, your car will use more fuel. In the worst scenario, your car engine might get damaged permanently. Hence, regular maintenance is necessary to prevent this scenario from happening. 

At the onset, your engine will fail to work at its optimum level, and its level of efficiency will begin to choke and deteriorate. If you let the issue persist, the engine will show more symptoms. 

Then, your engine might stall as the combustion system chokes. The problem becomes more severe if the engine exhibits knocking sound and overheats. There is a strong likelihood that the car engine will fail and become non-operational at this stage.


It is not enough to clean the external parts of your engine. What matters is that your car’s engine is clean inside. If it is not, it might choke and eventually fail to work. So, it will be best to do regular maintenance on your car engine. Make sure that the carbon deposits or buildups get cleaned. Besides, you need to change your driving habits, because your driving habits might contribute to the buildup of carbon in the engine. 

When it comes to maintaining your car engine, it will be best to be always on top of the situation. You can’t leave anything to fate or chance. Besides, you can avoid the predicament of engine failure due to the inordinate buildup of carbon deposits if you are assiduous in maintaining your car engine on a regular basis.