Phil, this is similar but not identical to what I experienced when my Crank Position Sensor went bad. It started as a "misfire" as you indicate, but mine was not consistent. It occurred within the first several minutes then ran fine. It then became difficult to start at times, and when it completely failed it shutoff while running and impossible to start. The sensor should output 1 volt when cranking, so you can do a quick check and see if that may be the issue. Good luck. Bob
