Re: Jeep 2000 grand Cherokee 6 cyl 4.0l 3rd cylinder missfire at
Welcome to the garage.
I would start doing a compression check on cylinder #3, to be sure its ok when cold.
What are the fault code(s) the PCM has stored? Most probably the P0303 (cylinder #3 misfire), but is there more? You could swap the injector #3 with an other position and see if the fault follows.
So if the engine warms up, cylinder #3 doesn´t start working by itself? You have to shut down and restart the engine to get it working? If the previous is ok, i would say that the problem is with the PCM.