How to Determine if a Car Spark Plug is Faulty?

[GabriellaLynn]

Spark plugs exhibit the following symptoms when they may be faulty: Difficulty starting the car, whether cold or hot, often requiring multiple attempts. Engine shaking occurs while driving. Reduced power output, noticeably weaker than usual. Increased fuel consumption. Stalling incidents. Failed exhaust emissions tests. Common causes and diagnosis of spark plug failures: Several situations can cause spark plugs to malfunction: Incorrect spark plug gap adjustment. A gap too small limits spark contact with the air-fuel mixture and suppresses flame kernel growth, resulting in weak sparks that struggle to ignite the mixture. A gap too large may exceed the ignition system's voltage capacity, preventing sparking. Cracked spark plug skirt. High-voltage current leaks through cracks, preventing sparking at the electrodes. Electrode carbon buildup causes current leakage around the center electrode instead of jumping to the side electrode. Excessive carbon accumulation shorts the spark plug, potentially burning the insulator and damaging the plug. Electrode damage. Prolonged electrical erosion or chemical corrosion from combustion gases can break electrodes, preventing sparking. Low spark plug insulation resistance. This reduces the ignition voltage across the spark gap, weakening or eliminating the spark. High-voltage wire short circuit. A leak in the ignition coil-to-distributor wire prevents entire engine startup; a distributor-to-spark plug leak affects only one cylinder. Burnt platinum contacts. This prevents all spark plugs from firing, making engine startup and operation impossible. Faulty spark plugs require prompt replacement. Replacement steps: Open the hood, remove the engine plastic cover, detach high-voltage wires while noting cylinder positions to avoid confusion. Remove spark plugs sequentially using a socket wrench, cleaning any external debris like leaves or dust. Insert new spark plugs, hand-tightening initially before final tightening with the wrench. Reinstall high-voltage wires in firing order sequence and replace the cover. Replacement interval: Typically 40,000-60,000 km under normal maintenance, but varies by brand and engine. Consult the owner's manual for specifics.