I have a 1990 XJ cherokee. I recently bought an engine out of a running and driving 1989 XJ. When I pulled the engine the casting # says 10-12-96. After I got it in my jeep it would start and idle perfectly, but when I give it gas it backfires through the intake and doesnt rev... I have checked the wiring and vacuum; changed the distributor, injectors, fuel rail & regulator, and the computer... I checked to be sure the timing was correct. Before I did the engine swap I had replaced the fuel pump and filter. Any help anyone can give me would be greatly appreciated!!!

 

Sounds like a plug wire might be mixed up, of the distribuitor might be off 180 degrees.

 

check firing order of spark plug wires