How to Check if a Car Spark Plug is Faulty?
2 Answers
If a spark plug exhibits the following symptoms, it may indicate a fault: Difficulty starting the car, whether cold or hot, often requiring multiple attempts. Engine shaking, noticeable while driving. Reduced power, feeling significantly less powerful than usual. Increased fuel consumption. Stalling. Failed exhaust emissions. Common causes and diagnosis of spark plug faults: Common issues that prevent spark plugs from working properly include: 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 difficulty igniting the mixture. A gap that is too large may exceed the ignition system's voltage capacity, preventing sparking. Cracked spark plug skirt. High-voltage current leaks through the crack, preventing sparking at the electrodes. Carbon buildup on electrodes, causing leakage from the center electrode to the surroundings instead of sparking to the side electrode. Excessive carbon buildup 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 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 or completely eliminating the spark. Short circuit in high-voltage wires. A leak in the wire from the ignition coil to the distributor can prevent the entire engine from starting. A leak in the wire from the distributor to the spark plug can prevent sparking in one cylinder. Burnt platinum contacts. This can prevent all spark plugs from sparking, making the engine unable to start or run properly. Faulty spark plugs should be replaced promptly. Replacement steps are as follows: Open the hood, remove the engine's plastic cover, and disconnect 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, checking for and cleaning any 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 reattach the cover. Spark plug replacement interval: Typically replaced every 40,000-60,000 km under normal maintenance conditions, but this may vary by brand and engine. Refer to the owner's manual for specifics.
As a DIY enthusiast car owner, I frequently inspect spark plugs to prevent malfunctions. First, turn off the engine and wait for it to cool down, then carefully remove the spark plug using a spark plug wrench. After extraction, examine the electrode tip: if it's covered in black carbon deposits, it indicates poor combustion, possibly due to a rich fuel mixture or engine overload; worn or deformed electrodes suggest the end of its service life; the gap should typically be between 0.8 to 1.0 mm—measure it with a feeler gauge, as gaps too wide or narrow can affect ignition. Lightly brush off carbon deposits with a small brush, but avoid damaging the insulator. When reinstalling, ensure the threads are aligned and apply the correct torque as specified in the manual—neither too tight nor too loose. Regular inspections can prevent roadside breakdowns; it's recommended to check every 20,000 kilometers. The condition of spark plugs affects fuel consumption and engine performance. Faulty spark plugs can cause engine misfires or difficulty starting—don't overlook this small but crucial component.
