I replaced the spark plugs & spark plug wires in my fiance's car this weekend (needed a tune up). When we fired up the car, all cylinders misfired (somewhat normal according to someone i know). Apparently, there is a film that has to wear off before the engine begins running smoothly. The engine did start running smoothly, and we took the car on a 3 hour trip yesterday. Today, the engine misfired again. Anyone know why this may be happening. Could it be possible the "film" hasn't completley worn off the new spark plugs? Or do you all think it's a different problem?