so I have a 2001 XJ, I recently swapped the motor and put a motor from a 2002 Jeep Grand Cherokee in it. Every thing was going fine for about 2 days after the swap and then all of a sudden my CEL starts flashing and the engine will not rev past 3000 rps. Neither in neutral or in drive. It also has a horrible ship and does not do this until the vehicle goes into limp mode. I have changed plugs, coil pack, injectors, map sensor, crank sensor, mass airflow sensor, and TPS. I have really ran out of things to do and I’m desperate at this point. I talked to a guy the other day and he was telling me that it may be a computer issue seeing as how the engine came out of a crane Cherokee. I don’t understand how that could be because all of the sensors are the same and plug right in to my harness now I did have to shave some ears down and tap some of them in a few places so that my brackets that I took off my Cherokee block would fit on my grand Cherokee block, including the motor mounts. If this is an ECU issue then how would I even begin to fix the issue. I mean it’s not like I can use an ecu from a grand Cherokee and if I get a new one for an xj then it’ll be the same thing I have now right? My ecu is good l, or at least it was when I pulled the old engine

Well the reason I swapped the motor is because cylinder 4 got completely destroyed when the piston came apart. I don’t really know what exactly caused that because it happened like two or three weeks after I bought the Jeep and I didn’t really see any signs. But I’ve checked all the grounds or at least the ones I know about. I checked the one coming off of the battery to the fender and the one on the back side of the engine that goes to the fire wall. I also checked the two on the passenger side of the block. They are all good. I also check my codes and it’s telling me multiple cylinder misfire. I don’t understand because I’ve changed all my injectors, plugs and my coil pack TWICE ����*♂️����*♂️ Here’s the thing that’s driving me insane, when it goes into limp mod that’s when it starts skipping and missing, before that it’s completely fine, no skip or miss what so ever. Usually if it starts doing that then I’ll cut it off and start it right back up and it’ll be fine for a few more minutes until it goes back to limp mode