What are the 8 states of spark plug combustion?
3 Answers
The following describes the states of spark plug combustion: 1. White or slightly white: A normally burning spark plug typically has a white or slightly grayish-white (brown or light gray) center electrode, with clean or slightly discolored ground straps. Carbon deposits can cause poor engine ignition. As carbon deposits generated during incomplete combustion adhere to the surface of the center electrode insulator, the dielectric layer, insulation layer, or shunt resistance of the insulator can be damaged. 2. Yellow: If the spark plug in use has lead deposits, the center electrode insulator will exhibit a yellow/brown characteristic, which may also lead to poor engine ignition under high speed and high load conditions.
The condition of spark plug combustion can indicate engine health. Through years of driving experience, I've summarized 8 common scenarios: During normal combustion, the spark plug tip is clean and symmetrical with an even brown color, indicating complete combustion. Carbon buildup shows as a completely blackened plug, meaning fuel isn't burning completely, and excessive carbon deposits can affect ignition. An oil-fouled condition has oil stains on the surface, possibly due to engine oil seal leakage. Overheated plugs have white or melted electrodes, suggesting the engine is running too hot and needs cooling. Pre-ignition damage shows pits or spots on the electrodes, indicating early ignition or knocking. Worn plugs have enlarged gaps and eroded electrodes, a natural result of prolonged use. Contaminated plugs may have green or red stains, possibly from coolant leakage corrosion. Improper gap setting leads to weak or unstable ignition, which may cause engine shaking. These 8 conditions can be diagnosed by observing spark plug color and shape. It's recommended to check them every 20,000 kilometers to prevent potential issues.
The 8 combustion states of spark plugs directly impact vehicle performance, which I pay close attention to during daily driving: A normally burning spark plug appears clean and tan-colored without abnormalities; Carbon deposits create blackened surfaces, indicating air-fuel ratio imbalance; Oil-fouled plugs covered in oil traces suggest engine oil leakage; Overheated plugs with whitened or melted electrodes may indicate cooling system failure; Pre-ignition damage shows pitted electrodes from incorrect ignition timing; Worn plugs have enlarged gaps weakening sparks; Contaminated plugs display colored stains (like green from coolant); Incorrect gaps cause ignition difficulties. Ignoring these can lead to fuel waste or sudden stalling. I routinely inspect them using my phone's flashlight, replacing any abnormal plugs immediately at repair shops to prevent unexpected breakdowns.
