1. Check if the engine can start normally
Check if the engine starts smoothly when cold, if there is obvious “frustration” and if it can ignite normally.
2. Check the engine vibration
Keep the car idling If the engine can run properly, it means the spark plug can work normally if the engine is intermittent or; vibration continues and makes an abnormal “chunking” sound, this means that there may be a problem with a certain spark plug and the spark plug needs to be replaced.
Detailed information:
Check the spark plug electrode gap : When removing the spark plug, you will find that the spark plug has a discharge electrode, and the electrode has normal consumption. If the deviation is too large, it will cause an abnormal discharge process (the normal deviation of thespark plug is 1.0 to 1.2 mm). in this case it will weaken your engine. At this point it needs to be replaced.
If there is a deposit between the top and the electrode, and the deposit is an oily substance, this proves that the cylinder is channeling oil and has nothing to do with the candle if the deposit is black; , this means that the spark plug has carbon deposits and is bypassing; The gray color deposit is due to additives in gasoline that coat the electrodes, causing misfires.
Baidu Encyclopedia-Ignition Coil