How to Measure the Condition of Spark Plugs?

[DelSawyer]

Spark plugs may indicate the following symptoms when they are faulty: Difficulty in starting the car, whether cold or hot, often requiring multiple attempts. Engine shaking, noticeable during driving. Reduced power, with a significant drop in performance compared to normal conditions. Increased fuel consumption. Stalling. Failed emissions tests. Common causes and diagnostics of spark plug failures: Several conditions can lead to non-functional spark plugs: 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 ignition difficulties. 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. Electrode carbon buildup, causing leakage from the center electrode to the surroundings instead of sparking to the side electrode. Excessive carbon deposits can short-circuit the spark plug, preventing sparks and damaging the insulator. Damaged electrodes. Prolonged electrical erosion or chemical corrosion from combustion gases can cause electrode breakage, rendering the spark plug non-functional. Low insulation resistance of the spark plug. This reduces the ignition voltage across the spark gap, weakening or completely eliminating the spark. 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 disable that cylinder's spark plug. Eroded 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. 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 each spark plug, checking for and cleaning any debris like leaves or dust. Insert the new spark plug into the hole, hand-tighten it first, then use the socket to secure it. Reinstall the high-voltage wires in the correct firing order and replace 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 type. Always refer to the owner's manual for specific recommendations.