So my old motor finally started showing it's age after 305000 miles. The jeeps original inline 6 started developing a knock about a week ago and over the weekend right after Thanksgiving I swapped the motor with one out of a 93 with around 190000 miles. After the swap I immediately noticed I had a misfire and attempted to diagnose the issue. (Note: prior to the swap the jeep ran perfectly) I figured out that cylinder 4 has a misfire. At first it was constant, but now it seems to be an intermittent issue. At first it was only at idle, but went away at higher rpms, then it just started misfiring intermittently regardless of rpms. It is definately more prevalent at idle and lower rpms, and sometimes I can get it to clear temporarily if I rev the engine. I think it has something to do with the #4 injector or it's wiring. Just looking for some pointers. Feel free to ask questions.

 

Update: I figured out the issue. It was a damaged spark plug. Not completely shot, but enough to cause intermittent issues, I had previously tested it, and I was getting consistent spark when I tested it, so I assumed it was good, but today when testing the injector I did the screwdriver test and could hear the injector clicking while the misfire was occurring, so I pulled the plug wire off and held it near the plug and could see that the ceramic had gotten damaged somehow. Replaced the plug, all is well with the world.