What Are the Symptoms of Faulty Spark Plugs in Sedans?

[MacPiper]

Spark plug failure manifests in the following ways: Difficulty starting the car, both during cold and warm starts, often requiring multiple attempts. Engine shaking, noticeable while driving. Reduced power output, feeling significantly weaker than usual. Increased fuel consumption. Engine stalling. Failed exhaust emissions. Common causes and diagnosis of spark plug failure: Several factors can prevent spark plugs from functioning properly: Incorrect spark plug gap adjustment. A gap too small limits the spark's contact area with the air-fuel mixture and suppresses flame kernel growth, resulting in weak sparks and ignition difficulties. 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, causing current leakage from the center electrode instead of jumping to the side electrode. Excessive carbon deposits can short-circuit the plug, damage the insulator, and ruin the spark plug. Electrode damage. Prolonged electrical erosion or chemical corrosion from combustion gases can break or detach electrodes, preventing sparking. Low insulation resistance. This reduces the voltage across the spark gap, weakening or eliminating the spark. High-voltage wire short circuits. Leakage between the ignition coil and distributor prevents all cylinders from starting; leakage between the distributor and spark plug affects only one cylinder. Burnt contact points. This prevents all spark plugs from firing, making the engine unable to start or run. Faulty spark plugs should be replaced promptly. Replacement steps: Open the hood, remove the engine's plastic cover, and detach the high-voltage wires, marking each cylinder's position to avoid confusion. Remove the spark plugs using a spark plug socket, cleaning any external debris like leaves or dust. Insert new spark plugs by hand first, then tighten with the socket. Reattach the high-voltage wires in the correct firing order and replace the cover. Replacement interval: Typically 40,000-60,000 km under normal maintenance, but varies by brand and engine. Refer to the owner's manual for specifics.