How is carbon buildup in cars formed?

[VonJackson]

Carbon buildup formation in cars: During engine operation, unsaturated olefins and gums in fuel produce a coking-like substance under high temperatures. This substance has oil-absorbing properties, causing incompletely burned gasoline to turn into carbon deposits again. Repeated accumulation makes the deposits thicker and thicker, leading to a vicious cycle. In mild cases, it affects engine idle speed and power performance; in severe cases, it causes mechanical damage to the engine and reduces its service life. Methods to reduce carbon buildup: Perform necessary cleaning of the car's intake system. In automotive maintenance, diagnosing intake manifold carbon buildup is very simple—just remove the throttle body to clearly see the extent of carbon buildup.

[SanAlessandra]

Speaking from my years of driving experience, let me talk about carbon deposits. Simply put, carbon deposits are like a layer of black grime inside the engine, mainly caused by incomplete fuel combustion. When the engine is running, the fuel injected by the injectors can't be burned 100%, and there are always some residues left. Especially when crawling in traffic jams, the engine doesn't reach optimal temperature, making it easier for unburned fuel residues to harden into deposits. Another issue is engine oil—over time, degraded oil can form coke on high-temperature components. My car used to shake during cold starts, and upon inspection, thick carbon deposits were found behind the throttle body. The mechanic blamed my frequent short trips—the engine was shut off before it could fully warm up, allowing carbon deposits to accumulate. City driving is the worst for carbon buildup, so it's best to occasionally take the car on the highway to blow it out.

[MacLucas]

Last time I accompanied a friend to get his car repaired, the mechanic explained how carbon deposits form while disassembling the engine. The sight was quite convincing: the piston tops were completely black with carbon residue. The technician said there are mainly three reasons: poor fuel quality with many impurities leaves more residue after combustion; infrequent air filter replacement allows dust to enter the combustion chamber and form deposits; and most critically, incomplete combustion at low temperatures. For example, during cold starts when the catalytic converter hasn't reached operating temperature, gasoline doesn't burn completely. The technician particularly mentioned that direct injection engines suffer more severe carbon buildup because gasoline is injected directly into the cylinders, unable to wash the back of the valves. He recommended checking combustion chamber carbon deposits every 20,000-30,000 kilometers.

[VonStephanie]

Carbon deposit formation is actually a pretty straightforward process. There are gum and olefins in gasoline, and when they undergo high-temperature combustion in the engine, if they don't burn completely, they can coke and deposit on metal surfaces. The most prone areas for buildup are the back of the intake valves, the tips of the fuel injectors, and the piston crowns. What I find most frustrating is that carbon deposits create a vicious cycle: when there's little buildup initially, it's manageable, but as the deposits thicken, they alter the combustion chamber's shape, reducing combustion efficiency and ironically producing even more carbon deposits. So, when you notice your car has sluggish acceleration, rough idling, or unexplained increases in fuel consumption, carbon deposits are likely the culprit. The good news is that this issue isn't too severe—regular use of fuel additives or professional cleaning can effectively resolve it.