cause or suspected reason for oil inside sparkplug wire receptacle through cover on 1990 Geo Prizm

pulled the sparkplug wires and the number one wire was literally drowning in oil(one closest to oil fill cap) the other three were dry and seemed fine dont know if this was from an internal problem or spill from the outside inspection i would say the oil is coming from an internal source to my knowledge no oil was spilled or other from the top

2 answers 2 comments
You really need to do the valve cover gasket with the spark plug o-rings as soon as possible, or you will be replacing the cat do to engine misfire.
what is the cat be more specific
CATALYTIC CONVERTER mucho denaro
REPLACING THE VALVE COVER GASKET SHOULD FIX THE PROBLEM. WE SEE ALOT OF THIS IN HIS TYPE OF SYSTEM