How to Distinguish Between Good and Bad Spark Plugs?
2 Answers
Methods to distinguish between good and bad spark plugs are as follows: Remove the spark plug and observe its appearance color to determine its condition: 1. If the spark plug is severely eroded, with phenomena such as blistering at the top, black streaks, cracks, or melted electrodes, it indicates that the spark plug is damaged and must be replaced immediately; 2. If it is black as if smoked, it indicates that the spark plug's heat range is incorrect or the air-fuel mixture is too rich, or engine oil is leaking; 3. If there are deposits between the top and the electrode, oily deposits indicate cylinder oil leakage, which is unrelated to the spark plug. Black deposits indicate carbon buildup on the spark plug causing a bypass, while gray deposits are due to additives in gasoline covering the electrode, leading to misfires; 4. A reddish-brown or rust color indicates that the spark plug is normal.
I think identifying good or bad spark plugs starts with their appearance, especially the electrode part. When I take out a spark plug, the first thing I check is the electrode gap—the standard gap is around 0.7-1.0 mm. If it's too large or too small, it indicates wear. If the electrode tip shows signs of burning, carbon buildup turning black, or oil contamination, it means the ignition efficiency has dropped. I remember last time when my car was slow to start, replacing the spark plugs made it run much smoother. It's like the heart of the car—too much dirt and it acts up. The ceramic insulator is also important; it should be free of cracks to be considered good. I recommend checking them every 30,000 kilometers, especially if you often drive in city traffic, as spark plugs can overheat and have a shorter lifespan. Regular maintenance checks can prevent future repair headaches.
