How to Identify if a Spark Plug is Damaged?
3 Answers
Methods to identify if a spark plug is damaged include: 1. Check whether the insulator skirt, electrode, and shell are covered with a layer of dark compound; 2. The engine feels sluggish while driving; 3. Loud popping sounds or black smoke during exhaust; 4. The vehicle idles roughly and is difficult to start; 5. The exhaust pipe turns black, accompanied by unburned fuel discharge; 6. The engine shakes rhythmically. Reasons for spark plug damage include: 1. Insufficient spark energy during ignition; 2. High air-fuel ratio in the fuel mixture; 3. Overheating of the engine; 4. Clogged air filter; 5. Excessively high idle speed; 6. Severe carbon buildup and use of low-quality gasoline; 7. Damaged valve oil seal or crankcase ventilation valve.
I've been driving trucks for over a decade, and I can tell if the spark plugs are bad just by driving. Symptoms like the engine hesitating during startup, difficulty igniting, lack of power when stepping on the accelerator, black smoke from the exhaust, or backfiring are pretty obvious. After turning off the engine, pull the wire and check the electrode gap of the spark plug—it should normally be between 0.8 to 1.0 mm. If it's too wide or shows signs of burning, it needs replacement. Too much carbon buildup, blackened electrodes, or oil contamination are also signs. I usually check them myself every 30,000 kilometers or so, using a multimeter to measure the resistance. If it exceeds 15 kilohms, it means the insulation is damaged. Don’t want to bother? Take it to a mechanic for diagnosis—don’t delay and risk damaging the engine. Safety comes first.
As an average car owner, I can detect spark plug issues from driving habits. Common symptoms include unstable idling, severe engine shaking, sluggish acceleration, or a sudden increase in fuel consumption. After stopping, open the hood and inspect the spark plugs—if the electrodes are charred or covered in thick carbon deposits, there's a problem. If they come out too easily, the sealing ring is damaged. Remember not to force them out to avoid damaging the wires. Regular maintenance and cleaning can extend their lifespan. For simplicity, have a professional shop handle it—saves time and effort.
