How to Know When Spark Plugs Need Replacement?
3 Answers
Methods to determine if spark plugs need replacement: Remove the spark plugs and observe them. Judge the condition of the spark plugs based on the following appearance colors. Normal spark plugs have a skirt insulator and electrodes that appear gray-white, gray-yellow, or light brown. A properly functioning spark plug has a skirt insulator that is reddish-brown, with an electrode gap between 0.8-0.9mm and no signs of electrode burn. If the spark plug is covered in oil or deposits but is not damaged, it can continue to be used after cleaning off the oil and deposits. If the spark plug is severely damaged, with signs such as blistering at the top, black streaks, cracks, or melted electrodes, the cause of the damage should be identified. After troubleshooting, replace the spark plug with a new one. Additionally, if the spark plug appears black as if smoked, it indicates the wrong heat range was chosen or the air-fuel mixture is too rich, with oil creeping up. If the spark plug is damaged, it can directly cause issues such as leakage in the vehicle's ignition system, increased fuel consumption, reduced power, and most importantly, difficulty in ignition, affecting the normal use of the vehicle. Severe erosion of the spark plug, blistering at the top, damage, or melted and eroded electrodes all indicate that the spark plug is ruined and should be replaced.
When spark plugs need replacement, I can clearly feel it in the driving experience. Last year when I was driving my old car, I encountered severe engine shaking, especially during startup or climbing hills—the car trembled like it was coughing, and acceleration became sluggish. Later, upon inspection, I found that the idle speed was unstable, with the needle jumping around, and fuel consumption had inexplicably increased by 15%. This was mostly due to spark plug electrode wear causing ignition failure. I tried removing the spark plugs to check—if there was black carbon buildup or white melting marks on the electrode tips, they definitely needed replacement. I usually pay attention to these symptoms and proactively replace them every two to three years or around 40,000 kilometers, rather than waiting until starting becomes difficult. Aging spark plugs can also damage the ignition coils, leading to higher costs. In short, by closely observing the car's daily responses, you can identify issues in time and keep the engine running smoothly.
When it's time to replace the spark plugs, I often feel the car lacks power during daily driving. For example, acceleration isn't as sharp as before, and the engine sometimes hesitates or makes a dull sound, as if it's half-asleep. This is more noticeable during cold starts—after ignition, the engine wobbles, and the idle speed needle on the dashboard fluctuates. I usually check them every two years, but if I drive more miles or frequently in the city, I pay extra attention. A simple way is to listen for uneven ignition sounds or test if acceleration feels sluggish at high speeds. Once, my car's fuel consumption suddenly increased, but after replacing the spark plugs, it immediately improved—just a small issue can have such a big impact. Regular maintenance is crucial; don't skimp on these costs to ensure safe and worry-free journeys.
