What are the symptoms of a faulty spark plug?
3 Answers
Spark plug failure manifests in the following ways: Difficulty starting the car, with both cold and warm starts being problematic, often requiring multiple attempts. Engine shaking occurs while driving the car. Reduced power output, with a noticeable decrease in performance compared to normal conditions. Increased fuel consumption. Engine stalling. Failed exhaust emissions. Common causes and diagnosis of spark plug failure: Several common issues can prevent spark plugs from functioning properly: Incorrect spark plug gap adjustment. A gap that is too small limits the contact area between the spark and the air-fuel mixture and suppresses flame kernel growth due to the quenching effect of the electrodes, resulting in weak sparks and difficulty igniting the mixture. 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 to leak from the center electrode to the surroundings rather than jumping to the side electrode. Excessive carbon deposits can short-circuit the spark plug, preventing sparking and potentially damaging the insulator. 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 reduces the ignition voltage applied to the spark gap, weakening the spark or completely eliminating ignition capability. 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 a spark plug can prevent sparking in that cylinder. Burnt platinum contacts. This can prevent all spark plugs from firing, making the engine unable to start or run normally. Faulty spark plugs should be replaced promptly. The 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 tighten it fully. Reinstall 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.
The spark plug is faulty. My car has recently been experiencing difficulty starting, requiring several attempts to ignite each time, especially noticeable when the engine is cold. At idle, the entire car shakes violently, making it feel like sitting in a rocking chair, resulting in a terrible driving experience. During acceleration, there's a noticeable lack of power—stepping on the gas pedal makes the engine roar, but the speed doesn't increase, making overtaking difficult. Fuel consumption has also significantly increased; previously, a full tank could cover 500 kilometers, but now it barely exceeds 400, costing much more. Occasionally, black smoke comes out of the exhaust pipe. After inspection, it was found that the spark plug electrode is worn out, causing poor ignition and incomplete combustion. Now, I get it serviced and replaced every 20,000 kilometers to prevent engine damage.
I enjoy tinkering with cars in my spare time, and faulty spark plugs show quite obvious symptoms. Extended cold starts or repeated attempts are needed, and severe idle shaking indicates unstable ignition. The acceleration response becomes sluggish, especially when climbing hills or under load, as the power can't keep up. The reason for increased fuel consumption is simple—poor ignition reduces combustion efficiency by 10%-20%. Regularly inspect spark plugs for gap and carbon buildup, and replace them promptly if worn. Don't wait until the ignition coil burns out, doubling repair costs—maintaining small components plays a big role in saving hassle and money.
