It could be the fuel to air mixture in the involved cylinder is higher or there could have been insufficient combustion over a period of time due to an electrical issue on that side. Think of the simple things first. Perhaps the spark plug went bad or if you use spark plugs with a removable terminal nut that big x wedge has a tendency to loosen them up quite a bit perhaps resulting in poor electrical conduction ( the affected side terminal nut loosening more significantly than the other side ). I use the Harley-Davidson equivalent spark plug for this reason because it’s terminal nut is fixed. Simple suggestions to think about before trouble shooting with a mechanic. Plugging into the ECU might provide some insight.
I think it could be an electrical issue, when I removed the fouled plug the top was loose. The new plug is tight so will see how that performs.
