In the dark, I can see a flashing light around all the spark plug holes. Some flash more often than others, with the lower two flashing more. I can't see any sparks, but I do see a glow. The engine runs fine and always has.......but is this normal?

No bites on your question yet so I'll pretend to know what I'm talking about and take a total shot in the dark... (someone please correct me!)



I'm not 100% sure I know what you are describing, but I wonder if you have a poor connection to the spark plugs and are producing arcing inside the boot.



Did you use some kind of dielectric grease on the spark plug cables? Suggested use is on the ceramic portion of the spark plug, and a small amount inside the cable boot fitting.



What is the relative humidity there? Arcing is more likely to occur with higher humidity. The dielectric grease helps maintain a dry connection.





[edit] --> The 2 lower (trailing) spark plugs fire twice as often as the top (leading) plugs