Common causes of spark plug malfunctions include the following: Incorrect spark plug gap adjustment. If the gap is too small, it not only limits the contact area between the spark and the air-fuel mixture but also suppresses flame kernel growth due to the quenching effect of the electrodes. Although a spark occurs, it is weak, making it difficult to ignite the mixture. Conversely, if the gap is too large, the ignition voltage provided by the ignition system may be insufficient to generate a spark across the electrodes. Cracked spark plug skirt. High-voltage current leaks through the crack, preventing sparking at the electrodes. Carbon buildup on the electrodes, causing the central electrode to leak current to the surroundings instead of sparking to the side electrode. Excessive carbon deposits on the spark plug can short-circuit it, preventing sparking and eventually damaging the insulator, leading to spark plug failure. Damaged electrodes. Prolonged electrical erosion from sparks or chemical corrosion from combustion gases can cause electrodes to break or detach, preventing sparking. Low insulation resistance of the spark plug. This condition reduces the ignition voltage applied to the spark gap, weakening the spark or even completely disabling the ignition function. Short circuit in the high-voltage wires. If the high-voltage ignition wire from the ignition coil to the distributor leaks, the entire engine may fail to start. If the wire from the distributor to the spark plug leaks, the spark plug in one cylinder may not fire. Eroded platinum contacts. This can cause all spark plugs to fail, preventing the engine from starting or running normally. Spark plug failures manifest in the following ways: Difficulty starting the car, whether cold or hot, often requiring multiple ignition attempts. Engine shaking, noticeable while driving. Reduced power, with a noticeable lack of acceleration compared to normal conditions. Increased fuel consumption. Stalling. Failed emissions tests. Faulty spark plugs should be replaced promptly. The replacement steps are as follows: Open the hood, remove the engine's plastic cover, and disconnect the high-voltage wires, marking each cylinder's position to avoid confusion. Use a spark plug socket to remove the spark plugs one by one, ensuring no leaves, dust, or debris are present, and clean the area thoroughly. Place the new spark plug into the spark plug hole, hand-tighten it a few turns, then use the socket to fully tighten it. Reinstall the high-voltage wires in the correct firing order and reattach the cover. Spark plug replacement interval: Typically, spark plugs should be replaced every 40,000–60,000 km under normal maintenance conditions. However, this may vary depending on the brand and engine type, so always refer to the owner's manual for guidance.
