Must Spark Plugs Be Replaced as a Set?

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Spark plugs must be replaced as a set because the discharge gap and resistance values differ between old and new spark plugs. Failing to replace all of them may result in issues such as engine shaking, difficulty in acceleration, and increased fuel consumption. Steps for replacing spark plugs: Open the engine hood, lift the plastic cover of the engine, and remove the high-voltage ignition wires. Mark the position of each cylinder to avoid confusion. Use a spark plug socket to remove the spark plugs one by one. While removing them, check for any external debris like leaves or dust and ensure they are thoroughly cleaned. Place the new spark plugs into the spark plug holes, hand-tighten them a few turns, and then use the socket to tighten them further. Reinstall the high-voltage ignition wires in the firing order and secure the cover. Methods to determine if a spark plug is damaged: Remove the spark plug and observe its condition based on the following appearance colors. A normal spark plug's insulator skirt and electrodes should appear grayish-white, grayish-yellow, or light brown. A properly functioning spark plug will have a reddish-brown insulator skirt, an electrode gap between 0.8-0.9mm, and no signs of electrode burn. If the spark plug is contaminated with oil or deposits but is otherwise undamaged, it can continue to be used after cleaning off the oil and deposits. If the spark plug is severely damaged, showing signs like blistering at the top, black streaks, cracks, or melted electrodes, the cause of the damage should be identified. After troubleshooting, replace the spark plug with a new one. Additionally, if the spark plug appears black as if smoked, it indicates the wrong heat range was selected, the air-fuel mixture is too rich, or engine oil is leaking into the combustion chamber.