Bad Fuel Injecter
On a 3.0 I had a misfire code on #4 along with a misfire in the first 1000 RPMs. After many resets of the two codes and ignoring the crank sensor advice from the parts store, I removed the plenum and swapped the 1 & 4 fuel injectors. Within 5 starts the codes were back but on the #1 not #4. After putting a new fuel injector in #1, the codes cleared by themselves on the 9th start and the code reader showed "Pass" on the 13th start. My question is why was the misfire in the first 1000 RPMs involved? The fuel injector was bad all the time, not just the first 1000 RPMs. What gives on this situation, it certainly confused the issue.