When Should Spark Plugs Be Replaced?

[MacDaniella]

Spark plugs should be replaced under the following circumstances: 1. Engine idling becomes rough; 2. Vehicle experiences poor acceleration with increased fuel consumption; 3. Difficulty in starting the engine; 4. Engine vibration when air conditioning is turned on. A spark plug mainly consists of a terminal nut, insulator, terminal stud, center electrode, side electrode, and metal shell, with the side electrode welded onto the shell. The function of a spark plug is to discharge high-voltage pulses delivered through the ignition wire, creating an electric spark by ionizing the air gap between its electrodes to ignite the air-fuel mixture in the combustion chamber. Under high voltage, the air between the center electrode and side electrode rapidly ionizes, forming positively charged ions and negatively charged free electrons.