What Does a Spark Plug Do?
Spark plugs are the heart of a car engine. The main function of the spark plug is to ignite the fire and ensure that the combustion process runs smoothly. Its electrodes produce a high-voltage arc that creates a spark that ignites the gas mixture in the engine cylinder.
As a result, the gas mixture in the cylinder explodes and burns. This pushes the piston into motion, which then turns the engine and allows the car to run normally.
Where Are the Spark Plugs in Your Car?

Refer to 4 in the picture, which is where your car’s spark plugs are located.
The exact position can vary by engine layout, but spark plugs are installed where they can ignite the air-fuel mixture inside the cylinder.
What Types of Spark Plugs Are There?
- Function typeBased on their function, spark plugs can be divided into non-resistive and resistive types. As automobile electronic control systems continue to develop and the use of electronic components increases, resistive spark plugs have become mainstream. They reduce electrode corrosion during discharge and minimize the impact of electromagnetic waves on in-car electronic equipment.
- Material typeSpark plugs come in different materials, such as copper core, single platinum, double platinum, and iridium. Each type is distinguished by the metal used at the tip. Precious metal spark plugs improve lifespan and enhance ignition reliability.
- Structure typeIn terms of structure, spark plugs can have single, double, triple, or quadruple side electrodes, though other less common configurations also exist.
6 Signs the Spark Plugs or Spark Plug Wires Need Replacing
Spark plugs play an important role behind the scenes as the heart of your car’s engine. However, heat build-up in the combustion chamber or a malfunctioning cooling system can cause the spark plug tip to overheat. Repeated overheating often leads to premature spark plug failure.
Damaged spark plugs show visible signs such as cracked insulators, worn electrodes, and carbon build-up. These issues, along with other indicators, signal when a spark plug needs replacement.
Regular Maintenance
Ordinary spark plugs may need replacement after 20,000-30,000 kilometers. Precious metal spark plugs last longer, typically needing replacement after 60,000 kilometers. In contrast, iridium spark plugs can last around 80,000 kilometers before replacement.
It is also important to check the color of the spark plugs and the contact gap every 3 years or after driving 60,000 kilometers. If the gap becomes too large, or if the surface shows obvious ablation or carbon deposits, consider replacing the spark plug.
Fuel Economy Degradation
Dirty or fouled spark plugs reduce fuel economy because they do not burn gasoline efficiently in the combustion cycle.
Slower Acceleration
If your car takes a long time to accelerate and lacks overtaking power, worn spark plugs may be the cause.
Rough Idling
Engine pinging, rattling, or knock-like noises, as well as strong vibrations, could indicate an issue with the spark plugs or spark plug wires.
Difficulty Starting
If the spark plugs do not produce enough spark to start the combustion process, the engine will not start. Other causes of hard starting include ignition system issues, a battery that needs replacement, or worn spark plug wires.
Warning Lights
Do not ignore the engine outline symbol or the check engine light. The warning lights will turn on if the spark plugs are faulty or if the spark plug wires need replacement.
Why Use a Spark Plug Tester?
These five questions have given us an introductory level of understanding of spark plugs. Next, let’s address the final question: how to choose a spark plug tester.
A spark plug tester is an essential diagnostic tool for any engine with a spark plug. It realistically simulates engine conditions and adjusts engine speed to test spark plugs for comparison. This allows you to directly observe the working condition of the spark plug.
The original article closes by noting that the next post will guide readers on how to choose the right spark plug tester.
Related Topics Mentioned in the Original Article
The original related list included several unavailable references and one external admin edit link. The titles are preserved below, but the backend edit URL is intentionally not kept in the frontend body.
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