Carbon buildup refers to a mixture accumulated on an engine's valves, combustion chamber, and intake manifold. It is formed when the engine's fuel is not fully combusted, resulting in hydrochloric acid and resinous gummy substances under high temperature and oxygen catalysis. These substances adhere to component surfaces and further condense into asphaltic and coke-like complex mixtures due to high temperature. Carbon buildup can be categorized into valve and combustion chamber buildup, and intake manifold buildup.
1. Two Common Types of Carbon Buildup
Valve and Combustion Chamber Buildup
Due to the control characteristics of electronic fuel injection engines, fuel is sprayed before ignition in each working cycle. When the engine is turned off, ignition is immediately cut off, but the sprayed fuel for that cycle cannot be reclaimed and adheres to the intake valve and combustion chamber walls. While gasoline evaporates quickly, the waxes and gummy substances in it remain. Over time, these substances accumulate and harden from repeated heating, forming carbon buildup. If the engine burns oil or if the gasoline quality is inferior, the buildup on the valves will be more severe and form faster. Since the structure of carbon buildup is sponge-like, a portion of the fuel sprayed into the cylinder after the buildup on the valve is absorbed, leading to a thinner mixture entering the cylinder. This can cause engine malfunctions, such as difficulty in starting, unstable idle, poor acceleration, backfiring when accelerating abruptly, exceeding emission standards, and increased fuel consumption. If more severe, it can cause valve sealing issues, resulting in a complete engine malfunction or even damage.
Intake Manifold Buildup
As the entire engine's pistons don't work synchronously, some intake valves can't fully close when the engine is turned off. Unburned fuel evaporates and oxidizes, leading to soft black carbon deposits, especially behind the throttle body in the intake manifold. This not only roughens the manifold wall, affecting airflow and the quality of the air-fuel mixture but also can block the idle passage, causing various engine issues.
2. Methods to Check for Carbon Buildup
Dismantling Method
Directly disassembling the engine to check for buildup. This method is time-consuming and can affect component performance and lifespan.
Endoscope Inspection
Removing spark plugs or injectors and using an endoscope to check for valve buildup. This method is convenient but costly.
Observing Feedback Voltage Changes
Using diagnostic computers to read the oxygen sensor's feedback voltage changes to indirectly detect buildup.
3. Several Methods to Reduce, Prevent, and Clean Carbon Buildup
Using High-Quality Gasoline
Higher-quality gasoline reduces the tendency of buildup formation. Drivers should refuel at reputable gas stations and occasionally add gasoline detergents to prevent and slowly remove existing buildup.
Avoid Extended Idling
Prolonged idling increases the time it takes for the engine to reach normal temperatures, accelerating buildup formation.
Drive on Highways and Adjust Shift RPM
Highway driving and raising the shift RPM can both help in preventing carbon buildup due to the increased airflow.
Use Fuel System Cleaners
Adding cleaners to the fuel system can help in cleaning the buildup from the fuel tank, pump, injectors, valves, and combustion chamber.
Mechanical Cleaning
Valve buildup cleaning is simpler, often requiring hand cleaning or soaking in a cleaning agent after removing the intake manifold. For cleaning buildup inside the engine cylinder, significant dismantling is required.
It should be noted that mechanical cleaning can degrade engine performance and should be done judiciously and preferably at professional service centers.
