My car has a misfire on the 4th piston. I wanted to fix this myself so I replaced the sparkplugs. I found oil on a sparkplug. What caused this? Please give me some advice on what to check and fix the issue.
Oil in the spark plug bore is caused by a leaking valve cover gasket. This can short out the spark plug and cause damage to the plug and coil, and also the spark plug boot. The valve cover gasket set needs to be replaced to correct the issue. You may want to enlist the help of a mechanic, such as one from YourMechanic, who will have the tools and training to replace the valve cover gasket for you.
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