What Causes Carbon Buildup During Idling?
2 Answers
Low RPM driving and poor gasoline quality can both lead to carbon buildup during idling. Main causes of carbon buildup: Traffic congestion. Heavy traffic is one of the causes of carbon buildup because the engine remains idling for extended periods, and frequent engine starts also contribute to carbon deposits. Using substandard gasoline. We advise against refueling at private gas stations and recommend choosing large state-owned enterprises like Sinopec or PetroChina to avoid incomplete combustion of low-quality fuel leading to carbon buildup. Poor driving habits. Many people prioritize fuel economy but neglect the need for synchronized engine RPM and throttle position, avoiding prolonged driving at low RPM with high gear. Hazards of carbon buildup: It can reduce engine power and increase fuel consumption; in severe cases, it may cause engine knocking, acceleration noise, damage to pistons and crankshafts, and even lead to oil burning requiring major engine overhaul; it directly affects vehicle emissions, potentially causing failure in annual inspection tests.
After repairing cars for over a decade, I've found idle carbon buildup is particularly common, with the core issue being low combustion efficiency. At idle, the engine temperature doesn't rise sufficiently, fuel atomization is poor, and the air-fuel mixture simply doesn't burn completely. Look at vehicles frequently used for school runs - idling with AC on for half an hour while waiting, and you'll find the intake manifold coated in black sludge when opened. The fuel injectors suffer most, continuously spraying tiny fuel droplets that stick to valves, accumulating over time like burnt rice crust. I recommend turning off the engine at traffic lights exceeding 60 seconds, regularly taking highway drives to rev the engine, and using walnut shell blasting for intake system cleaning every 20,000km on older vehicles. The carbon deposits behind the throttle body most affect performance - you can actually feel the rough granular texture with your fingers.
