What are the symptoms of a faulty spark plug in a car?

[VonPiper]

Spark plug failure manifests in the following ways: Difficulty in starting the car, both cold and hot starts are problematic, often requiring multiple attempts. Engine shaking occurs while driving. Reduced power output, noticeably weaker performance compared to normal. Increased fuel consumption. Engine stalling. Failed exhaust emissions. Common causes and diagnosis of spark plug faults: Several common situations can cause spark plugs to malfunction: Incorrect spark plug gap adjustment. A gap that's too small limits the contact area between the spark and the air-fuel mixture while suppressing flame kernel growth due to the electrode's flame-quenching effect - even if sparking occurs, it's weak and mixture ignition becomes difficult. Conversely, a gap that's too large may exceed the ignition system's voltage capacity, preventing spark generation. Cracked spark plug skirt. High-voltage current leaks through cracks, preventing sparking at the electrodes. Electrode carbon buildup causes current leakage from the center electrode rather than jumping to the side electrode. Excessive carbon accumulation shorts the spark plug, preventing sparking and potentially damaging the insulator. Electrode damage. Prolonged electrical erosion from sparks or chemical corrosion from combustion gases can break electrodes, rendering them incapable of sparking. Low insulation resistance in spark plugs. This condition reduces the ignition voltage across the spark gap, weakening or completely eliminating spark generation. Short circuit in high-voltage wires. Leakage in the coil-to-distributor wire prevents entire engine starting, while distributor-to-spark plug wire leakage affects individual cylinders. Eroded platinum contacts. This condition prevents all spark plugs from firing, making engine starting and operation impossible. Faulty spark plugs require immediate replacement. The replacement procedure is as follows: Open the hood, remove the engine's plastic cover, and detach high-voltage wires while marking their positions to avoid confusion. Remove spark plugs sequentially using a spark plug socket, cleaning any external debris like leaves or dust before removal. Insert new spark plugs by hand initially, then tighten with the socket. Reinstall high-voltage wires according to the firing order and replace the cover. Spark plug replacement interval: Typically 40,000-60,000 km under normal maintenance, though this varies by brand and engine type. Always consult the owner's manual.