Bad Valve Cover Gasket Leak. Sometimes when oil leaks from a valve cover gasket it leaks all the way down to the spark plug galley and eventually seeps inside the spark plug tubes. This will cause a misfire or reduce engine.
Clogging the drainage holes and placing a lot of pressure on the gasket. Think about what you just said. A very small dab of gasket sealer may be applied to the covers in four or five locations to hold the gaskets in place during installation if desired.
Your valve cover gasket may be leaking for a variety of reasons.
If your car has a plastic cover over the valve covers remove it so you can inspect your valve cover gasket. During most oil changes the technician will inspect the valve cover to see if there is any leaking oil coming from the valve cover gasket. It could be shrunken cracked or rotten or your valve cover itself may be cracked or broken or one of the valve cover bolts may just be loose allowing a little leak. There is no chance of repairing a bad gasket.