What are the symptoms of a faulty spark plug?

[Theresa]

Symptoms of spark plug failure include: Difficulty starting the car, with both cold and hot starts being problematic, often requiring multiple attempts. Engine shaking, where the car exhibits noticeable vibrations while driving. Reduced power, with a clear sensation of diminished performance compared to normal operation. Increased fuel consumption. Stalling incidents. Failed exhaust emissions tests. Common causes and diagnostics of spark plug failure: Several factors can lead to spark plug malfunction: Incorrect spark plug gap adjustment. A gap that is too small limits the contact area between the spark and the air-fuel mixture, and the quenching effect of the electrodes suppresses flame kernel growth, resulting in weak sparks and ignition difficulties. Conversely, a gap that is too large may exceed the ignition system's voltage capacity, preventing sparking between the electrodes. Cracked spark plug skirt. High-voltage current leaks through the crack, preventing sparking at the electrodes. Carbon buildup on electrodes, causing current leakage from the center electrode to surrounding areas instead of jumping to the side electrode. Excessive carbon deposits can short-circuit the spark plug, preventing sparking and damaging the insulator. Damaged electrodes. Prolonged electrical erosion from sparks or chemical corrosion from combustion gases can cause electrode breakage, rendering the spark plug inoperative. Low insulation resistance of the spark plug. This reduces the ignition voltage applied to the spark gap, weakening or completely eliminating the spark. Short circuit in high-voltage wires. Leakage in the wire from the ignition coil to the distributor can prevent the entire engine from starting, while leakage in the wire from the distributor to the spark plug can prevent sparking in one cylinder. Eroded platinum contacts. This can cause all spark plugs to fail, preventing engine start and normal operation. Faulty spark plugs should be replaced promptly. Replacement steps are as follows: Open the hood, remove the engine's plastic cover, and detach 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 the surrounding area is free of debris like leaves or dust. Insert the new spark plug into the hole, hand-tighten it a few turns, then use the socket to secure it. Reattach the high-voltage wires in the correct firing order and replace the cover. Spark plug replacement interval: Typically, spark plugs should be replaced every 40,000 to 60,000 kilometers under normal maintenance conditions, but this may vary by brand and engine type. Always refer to the owner's manual for specific recommendations.