Ive got a 90 jeep cherokee 4x4 4.0L with a new rebuilt jasper engine that a few friends and i just installed, its the second engine we have replaced in this jeep cuz im jus a lil hard on em. But anyways, we started it for its first time in the new jeep, and it fired!!! wow thats a first lol, but anyways during the "fine tuning" part to get everything str8nd around and running right i noticed that it wont rev past 2000rpm while slightly on the throttle, it kind of acts as if it has a rev limiter but i kno that isnt the case, but if i punch it to the floor it runs like a raped ape, just like it should. lol it backfires and kind of "bounces" at that certain rpm until i open it up completely and then it clears up, but it isnt even driveable on public roads, wont go over 25mph without backfiring and sputtering unless i floor it and it runs puuuurfect idleing, weve tried rerouting vaccum lines, unhooked the egr valve, new cap, rotor, plugs and wires, its getting constant 32-35lbs of fuel pressure on the fuel rail while idleing or revving, new crank position sensor, new coil, new map sensor. the engine came from a 89 jeep cherokee, we havent tried swapping the computers yet, but the wierd thing is is that i can completely unhook every wire from the "throttle body", and it will run the exact same way, no change. idk where to go from here. HELP

 

make sure that the plastic guide is placed on the very bottom of the pump and the rubber grommet goes on next, then make sure the small sock filter lines up perfect with the square area down inside the module, look down in it very,very important, now the other number one cause that hundreds of jeep owners are going through with all the same issues other than not installing the plastic guide and sock filter is make sure when you take your fuel pressure regulator ,the one that is clipped down in the top of your fuel module,over the fuel pump, when you remove the regulator there is a tiny 1/4 inch rubber o
ring that is attached at the very tip of the pressure regulator look down in the top of the module and remove it if it's not attached to your regulator .the new regulator will come with one on it.if you pulled your old regulator out to check it or replace it that day lil o ring stuck in there will cause your jeep to starve for gas if you don't have it on the regulator when you replace it.same with the plastic guide on the fuel pump and small sock filter make sure it lines up with the offset square area in the bottom of the module also make sure the large sock filter is on the outside bottom.all you jeepers this is Ronnie Wilburn , I sol bed the impossible. You are all very welcome

 

Click on the Pink Link in my Tips below and do 12 and 13.

 

That was my thought. Distributor not indexed properly.