How to Determine the Quality of Spark Plugs?
2 Answers
Methods to determine the quality of spark plugs: 1. Spark Test: Remove the spark plug and place it on the cylinder block for a high-voltage line test. If there is no spark or the spark is weak, it indicates that the spark plug is leaking or not working. 2. Color Observation: After removing the spark plug, if the surface appears reddish-brown or rust-colored, it indicates the spark plug is normal. If it is oily, it suggests the spark plug gap is misaligned, there is excessive fuel supply, a short circuit in the high-voltage line, or the spark plug is not working. If the spark plug is severely eroded, with phenomena such as pitting, black streaks, cracks, or electrode melting at the top, it indicates the spark plug is damaged and must be replaced immediately. Effects of a Bad Spark Plug: If a spark plug is damaged, it can directly cause issues such as leakage in the vehicle's ignition system, increased fuel consumption, and reduced power. The most significant impact is difficulty in ignition, affecting the normal operation of the vehicle. Severe erosion of the spark plug, with pitting, damage, or melting and erosion of the electrode at the top, indicates that the spark plug is destroyed and should be replaced.
When I first bought the car, it often had trouble starting smoothly and would shake a bit during acceleration. I initially thought it was due to poor fuel quality, but later, a car-savvy friend told me it might be a spark plug issue. He taught me to first pay attention to the engine's response while driving—like unstable idling or a sudden increase in fuel consumption—as signs to be suspicious. Then, open the hood, remove the spark plug, and inspect its condition: under normal circumstances, the electrode should be a clean brownish color. If you see excessive black carbon deposits, worn or deformed electrodes, cracks, or a noticeably enlarged gap, it’s definitely time for a replacement. I once measured the gap myself—using calipers, the ideal gap is around 0.8 mm; anything too large or too small affects ignition. Lastly, I remember that faulty spark plugs not only waste fuel but can also harm the engine. So, it’s best to proactively check them every 20,000 to 30,000 kilometers rather than waiting for a major problem. This habit has saved me a lot of unnecessary expenses.
