Common reasons for spark plug failure 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. If the gap is too large, the ignition voltage provided by the ignition system may be insufficient to create a spark across the electrodes. Cracked spark plug skirt. High-voltage current leaks through the crack, preventing a spark from forming at the electrodes. Carbon buildup on the electrodes. This causes the central electrode to leak current to the surroundings instead of sparking to the side electrode. Excessive carbon deposits can short-circuit the spark plug, preventing it from 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 the electrodes to break or wear away, preventing sparking. Low insulation resistance of the spark plug. This 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 wire. 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 spark. Burnt or eroded platinum contacts. This can cause all spark plugs to fail to spark, preventing the engine from starting or running normally. Symptoms of spark plug failure include: Difficulty starting the car, whether cold or warm, often requiring multiple attempts. Engine shaking or vibration while driving. Reduced power, with noticeably weaker acceleration than usual. Increased fuel consumption. Engine stalling. Failed emissions tests. Faulty spark plugs should be replaced promptly. The replacement steps are as follows: Open the hood and remove the engine's plastic cover. 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. Check for debris like leaves or dust around the area and clean it thoroughly. Insert the new spark plug into the hole, hand-tighten it a few turns, then use the socket to tighten it fully. Reinstall the high-voltage wires in the correct firing order and reattach the cover. Spark plug replacement interval: Under normal maintenance conditions, replace them every 40,000 to 60,000 kilometers. However, this may vary depending on the brand and engine type, so always refer to the owner's manual.
