Hello everyone my name is Sergio i have a 1999 jeep grand cherokee laredo with the 4.0 straight 6. Recently i replaced the engine and tranny, it started for while would run fine until i hit the throttle then it would just act like it was choking and die out, now it wont start at all it back fires out of the intake when i try to start it. If anyone has any idea of what this can be please let me know thanks in advance

 

You may have damaged the crank sensor when installing the engine. That's where I would start looking.