What do Automotive Spark Plugs do?

1. The function of automobile spark plug

The most fundamental function of Automotive Spark Plugs is to generate an electric spark at the most appropriate moment to ignite the combustible mixture (a mixture of gasoline and air) in the cylinder.

Intake and compression: The engine's piston moves downward, sucking in a mixture of gasoline and air. The piston then moves upward, violently compressing this mixture.

Ignition moment: When the mixture is compressed to the densest and highest temperature, the engine computer (ECU) will issue instructions, and the ignition system will generate tens of thousands of volts of high-voltage electricity and deliver it to the spark plug.

Spark generation: High-voltage electricity breaks down the gap between the two stages of the spark plug, producing a strong electric spark.

Ignition and deflagration: An electric spark instantly ignites the compressed mixture, causing it to burn violently (similar to a small explosion) and generate huge pressure.

Generate power: This pressure pushes the piston downward, which drives the crankshaft to rotate through the connecting rod, thus providing forward power for the car.

To put it simply: the job of a spark plug is to convert electrical energy into sparks, and ultimately chemical energy (gasoline) into mechanical energy (power).

2. Characteristics of a “good” spark plug

Because of its extremely harsh working environment (high temperature, high pressure, chemical corrosion), a high-quality spark plug must meet:
Precise flashover timing: The spark must be generated within a precise time of one thousandth of a second.
Sufficient spark intensity: The spark must be strong enough to successfully ignite in a severely compressed mixture.
Heat resistance: The tip must be able to withstand the instantaneous gas temperature of over 2000°C, and the skirt must be able to conduct heat away to avoid overheating itself.
Strong corrosion resistance: Resistant to chemical corrosion caused by fuel additives and combustion products.
Excellent insulation: ensure that high-voltage electricity only jumps through the electrode gap and does not "leakage".

3. What problems will occur if the spark plug fails or is in poor condition?

If the spark plug performance is degraded or damaged, it will not be able to effectively complete its core task, resulting in:
Ignition failure (misfire): A certain cylinder does not work at all, and the power will be significantly reduced.
Difficulty cold starting: Difficulty starting the engine in the morning or after being parked for a long time.
Idle vibration: The engine vibrates obviously and is unstable when the engine is stopped and waiting for a red light.
Weak acceleration and frustration: When stepping on the accelerator, the car feels "sluggish" and jerks around.
Increased fuel consumption: Due to insufficient combustion, part of the gasoline is wasted and emitted with the exhaust.
Exceeding emission standards: Insufficient combustion will lead to an increase in harmful exhaust gases (such as HC hydrocarbons) and may fail the annual inspection.