I have a 98 F-150 with a 4.6, It started to miss fire on friday night,as of monday night I started to change my spark plugs when I noticed the Passenger side plugs where all covered and sitting in oil. Drivers side plugs seemed a lil bit rusty. Does this mean I have a blown head gasket or valve cover gasket?? When the truck warms up, it runs fine, when cold it miss fires. The plugs and wires where installed in summer of 04 and the truck has 20k miles on the newer plugs and wires. I did a compression test and all the cylinders where between 150-160. The heater core hoses does not leak, It seems like a valve cover gasket is leaking on the top side into the spark plug sockets. The anti-freeze has no oil in it. I'm stummped on this, Thanks for any help Mike

 

Sounds to me like you found the problem... Change the valve cover gasket and you should be good to go...

 

So hopefully its just a valve cover gasket? Nothing internally should be messed up? Well I will let every one know the outcome, thanks Mike