Yes that will cause a misfire. Im thinking your plugs are in the middle of the valve cover. If so you need to replace valve cover gasket and do tune up.
I did a tune up on it. Made it a lil better. But still getting oil in spark plug. what causes the oil to get undre the spark plug?
The valve cover gasket is almost surely your problem. Only after I actually had it in front of me could I be more sure.