This condition will cause a misfire. This can be also caused by changing oils in midstream. This plug is oiled fouled, caused by poor oil control. Check for incorrect heat range plug, over advanced timing, lean fuel mixtures or even hot spots or deposit accumulation inside the combustion chamber. Check for incorrect heat range plug, over advanced timing, lean fuel mixtures or even hot spots or deposit accumulation inside the combustion chamber.
Splashed deposits look as if they are small islands of contaminants on the insulator.
This is usually caused by dirty carburetor bores or air intake.