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What Causes Carbon Build Up In Engines – Causes You Must Know!

Dealing with carbon buildup in the engine can give you big-time stress. As nobody wants poor acceleration, cold stalling, and engine misfires to ruin their driving experience.

There is no other way that you can fix this problem without knowing what causes carbon buildup on pistons, valves, and cylinder heads, and so on. That can literally save your engine.

Did you ever think about the facts that trigger this horrific amount of carbon deposits? Then say no to all the worries as we are here to help you out with all the information about the causes of carbon buildup.

What causes carbon build up in engines

Some engines are more likely to get filled with buildups. On the other hand, road conditions traffic, and even bad fuel can cause carbon buildup.

To protect engines and save the carbon buildup cleaning cost you should be aware of what causes carbon build-up on intake valves and other engine components. Here are the reasons behind carbon deposits:

GDI engines

Unlike others, GDI engines spray the hydrocarbons directly in the combustion chamber. That’s why direct injection vehicles are prone to have carbon buildup.

Having detergent features to work as a cleaner isn't that helpful. Because when the direct sprayed gas is not going through the intake manifold, it starts the carbon buildup formation process.


When the fuel-burning starts inside the combustion chamber the gasses travel through the gap between the pistol ring and sleeve. Then the buildup happened because of the PCV system.

In PCV for avoiding the formation of pressure down in the crankcase, the gas is being filtered to send back into the system. But the filtrations process leave some amount of deposits in there.

EGR system

In modern engines, the exhaust valve gas takes a U-turn to the intake manifold. The ECG system is the main culprit behind the carbon getting buildup.

Exhaust gas has carbon in it which deposits on the wall. For upgrading the car from euro 3 to euro 4, engines have EGR systems.

Leakage of oil

Leakage of oil through the wall sealing is also another cause of forming residues. Because the leaked oil runs all over the engine.

When the oil slides from the sleeves to the crank base, it returns into the intake manifold. The oil sits on the valves to create buildups.

In addition to what causes carbon build up?

  • Personal driving habits and forced speed limit affects the engine in a bad way.
  • Traffic issues like stopping or starting the car again and again within a short period trigger the formation of carbon buildup.
  • The combustion procedure doesn’t happen so smoothly because of the bellow the required standards or low-quality fuel. Then the engine end up depositing carbon everywhere.
  • Sometimes drivers lead the car in an overfill situation by slamming the throttle while running. At that time, carbon deposits in engine can occur due to unburned gasoline.
  • The idle speed of the engine causes incomplete combustion and deposits of carbon.
  • Manual cars can show low-speed high-speed or high-speed low-speed driving problems because of the forgetful nature while shifting the gear in those cars. That can leave residues in the engine components.

Fixing carbon buildup:

If you notice any carbon buildup in engines symptoms in your engine, then don't be late. Here are the steps about how to fix carbon build up in engine:




Dismantle all the parts like muffler, batteries to get access to the cylinder  


Liftoff the cylinder head gently


Get rid of the old gasket


Scrap off the buildup using a wooden or plastic scraper


Dip in the cleaning solution for 20 minutes to dissolve all the gunk


Make the valves carbon deposits free


Look for all leftover buildup in  the engine components


Do 2nd step cleaning if needed.


Reassemble all the parts you took off earlier


Final Words

With enormous advantages of upgraded modern engines comes with the huge problem of carbon deposits. Like oil leaking, PCV, and EGR system plays a vital role in that.

Higher compression ratio due to the reserved space inside the combustion chamber by carbon buildup can damage your engine. But having good knowledge about the reasons can make the prevention easier.

So don't make any move in hurry. Hope you’ll consider digging into the reasons before taking any actions.

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