How to Check if Spark Plugs are Damaged?

[SophiaFitz]

Spark plugs exhibit the following symptoms when they may be faulty: Difficulty in starting the car, both cold and warm starts are challenging, often requiring multiple attempts. Engine shaking occurs while driving. Lack of power during driving, noticeably weaker than usual. Increased fuel consumption. Stalling issues. Failed exhaust emissions. Common causes and diagnosis of spark plug failures: Several situations can cause spark plugs to stop working: Incorrect spark plug gap adjustment. A gap too small limits the contact area between the spark and the air-fuel mixture and suppresses flame kernel growth due to the electrode's quenching effect, resulting in weak sparks and difficulty igniting the mixture. A gap too large may prevent the ignition system from providing sufficient voltage to create a spark between the electrodes. Cracked spark plug skirt. High-voltage current leaks through the crack, preventing sparking at the electrodes. Electrode carbon buildup, causing the center electrode to leak current to the surroundings instead of sparking to the side electrode. Excessive carbon deposits can short-circuit the spark plug, preventing it from sparking and damaging the insulator. Damaged electrodes. Prolonged electrical erosion from sparks or chemical corrosion from combustion gases can cause electrodes to break off, preventing sparking. Low insulation resistance of the spark plug. This reduces the ignition voltage applied to the spark gap, weakening the spark or completely disabling ignition. Short circuit in high-voltage wires. If the ignition coil-to-distributor high-voltage wire leaks, the entire engine won't start. If the distributor-to-spark plug wire leaks, one cylinder's spark plug won't spark. Burnt platinum contacts. This prevents all spark plugs from sparking, making the engine unable to start or run normally. Faulty spark plugs need timely replacement. Replacement steps are as follows: Open the hood, remove the engine's plastic cover, and detach 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 external 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 firing order and replace the cover. Spark plug replacement interval: Normally replaced every 40,000-60,000 km under proper maintenance, but this varies by brand and engine. Refer to the owner's manual for specific recommendations.

[DiLola]

Check if the spark plugs are damaged. I often judge this while driving myself. Faulty spark plugs can cause severe engine shaking, especially noticeable during idling or acceleration when the car jerks repeatedly. If it takes several attempts to start the engine or if the idle is unstable with fluctuating RPMs, these are likely signs of spark plug issues. The most direct method is to remove and inspect them: wait for the engine to cool down, disconnect the ignition coil, use a spark plug wrench to remove the plug, and examine the electrode. A normal electrode should be grayish-white or light brown. If you notice black carbon buildup on the center electrode, it indicates incomplete combustion, requiring cleaning or replacement. If there’s oil residue or a wet appearance, the seal might be leaking. Also, check for electrode wear—if the gap is noticeably wider or deformed, the plug is no longer usable. Additionally, a sudden increase in fuel consumption is another warning sign. I’ve experienced this before—my fuel consumption spiked by 20%, and replacing the spark plugs fixed the issue. It’s recommended to inspect them every 30,000 kilometers to avoid severe damage to critical engine components.

[McSilas]

Checking spark plugs as part of routine maintenance is quite simple. First, turn off the engine and let it cool for at least half an hour—safety first. Then, disconnect the ignition coil wires and use a spark plug socket wrench to remove the spark plugs. Hold them in your hand and inspect carefully: the electrodes should be clean and free of cracks. If there's excessive carbon buildup, like black, crusty deposits on the surface, it indicates an issue with the fuel-air mixture, and the spark plugs aren't functioning properly. If you notice oil stains or a burnt smell, it might suggest cylinder oil leakage or coil failure. Next, use a feeler gauge to measure the gap—ideally around 0.8mm. If it's too wide or deformed, replace them immediately. I make it a habit to check quickly during every service because faulty spark plugs can cause ignition failure, weak acceleration, or even leave you stranded on the road. Pay attention to exhaust smoke color—excessive black smoke is another warning sign. When replacing spark plugs, always choose the correct model and avoid cheap options to prevent engine performance issues.

[StLydia]

Identifying a faulty spark plug isn't difficult; the key is observing engine behavior. If starting becomes problematic—requiring repeated ignition attempts when turning the key—or if the car experiences sudden jerking while driving with sluggish acceleration, these symptoms point to spark plug failure. Unstable idle RPM, fluctuating like a dance, is another common indicator. Additionally, check the exhaust pipe: black smoke signals incomplete combustion, suggesting the spark plug may not be firing properly.

For DIY inspection: remove the spark plug to examine its condition. A healthy one should have dry, clean electrodes with minimal wear. Cracks, heavy carbon deposits, or melted traces mean replacement is due. Using a multimeter to measure resistance helps too—standard values range between 4-15 kilohms; readings outside this range indicate internal issues. Without tools, listen for abnormal popping sounds during ignition.

Regular replacement (typically every 20,000-50,000 km) prevents minor issues from escalating into major repairs.