I have a 98 Crown Vic with about 147,000 on the car about 35,000 on the engine, bought this car from a friend (fairly reliable friend) for the dirt cheap price of 500$ so I am expecting a few problems. So here are my issues so far with the car, was getting a check engine light with code p0308 and having valve clatter upon acceleration when at normal running temperature. I have Replaced the fuel filter and run fuel system cleaner through a few full tanks of gas. (did this first because car sat for a few months before i purchased it) I have checked the coil packs they seem to be fine not throwing any sparks and are in good condition. I have pulled all of the plugs and cylinder 7-8 spark plugs had oil on them (not at the tip though). replaced those 2 with new plugs as the rest look to be in good shape, I know i need to replace all of them but am trying to solve the valve clatter. In doing these things after i unhooked the battery to clear the CEL its hasn't came back but am still experiencing valve clatter. I have check the air hoses for leaks none were found. cooling system seems to be running fine not leaks not overheating, no oil in water or water in oil. Just looking for a little guidance as to where I should start from here. Other than the valve clatter the car runs great does start up rough every so often.