1997 Mercury Grand Marquis LS 8 Cyl 4.60L
Why would there be oil and coolant in my spark plug sockets?
There has been sputtering and backfiring. Also a rotten egg smell. I changed the fuel filter, PCV valve, and plugs and wires. Noticed oil and coolant mixed in spark plug sockets. New plugs still misfire.
I suspect that it is oil from a leaky valve cover gasket. Replace the valve cover gaskets, the ignition wires and the spark plugs. If it really is coolant in there and you clean it out and it returns, then I suspect the intake manifold gasket is leaking coolant externally and it is entering the spark plug tubes from the top.