What are the symptoms of a faulty spark plug in one cylinder of a four-cylinder engine?

[LucasDella]

Damaged spark plugs may exhibit the following symptoms: difficulty starting the engine, reduced power, excessive exhaust emissions, and increased fuel consumption. Steps for replacing spark plugs: Open the engine hood, remove the plastic cover of the engine, detach the high-voltage ignition wires, and mark each cylinder's position to avoid confusion. Use a spark plug socket to remove the spark plugs one by one. While removing them, check for external debris such as leaves or dust and ensure thorough cleaning. Place the new spark plug into the spark plug hole, hand-tighten it a few turns, and then use the socket to tighten it further. Reinstall the high-voltage ignition wires according to the firing order and secure the cover. Spark plug replacement intervals: Under normal maintenance conditions, spark plugs should be replaced every 40,000 to 60,000 kilometers. However, this may vary depending on the brand and engine type, so it's advisable to follow the owner's manual. Refer to the following standards for maintenance replacement: Platinum spark plugs should be replaced at 40,000 kilometers, standard nickel alloy spark plugs at 20,000 kilometers, and iridium spark plugs at 60,000 to 80,000 kilometers.