The valve seals can potentially cause an engine misfire if the engines valve seals are leaking and causing engine oil to seep past them and get into the combustion chamber.
The oil can also foul the spark plugs or reduce the engines spark from the spark plug which can cause the misfire.
Other things that can cause an engine misfire are bad spark plugs, bad spark plug wires, bad ignition coils or bad ignition coil, bad distributor cap and rotor, bad ignition module or even the engine can be out of time.
You can pull your spark plugs to see if they have some oil on them and if so then the engine is burning oil and possibly due to bad valve seals.
If you have Blue/gray exhaust smoke then it's a sign that your engine is burning oil and could be caused by the bad valve seals or also could be bad piston rings that are worn and need replaced.