99 4.0 auto.
So me and my dad dragged home a blown up 99 Cherokee to fix for my sister to drive. We swapped the engine out of a 95 into it. We swapped over all the sensors, the intake, the exhaust, pretty much only used a short block.The engine ran in the 95 but couldn't be driven because it was wrecked. now we got it all back together and it runs like crap, missing, backfiring and stalling. The check engine light hasent come on and we'v checked for vacuum leaks several times. I'm running out of ideas. Any suggestions?

 

Could be many things, but one of the primary causes of crappy start, backfires, and stalling after a swap is having the spark plug order incorrect. If you used an image off the web, or a Haynes manual, you might have gotten bad information (there are more incorrect images on the web for this than correct ones).

When looking from the front of the vehicle, the distributor post at the 8oclock position is 1 and goes 1-5-3-6-2-4 (cylinder closest to front of vehicle is 1). Make sure you have this correct before pulling your hair out on other things.

This post has images:
https://www.cherokeeforum.com/f2/mes...-order-225475/

 

I agree with Jordan - sounds like distributor related. Did you remove the distributor on the new engine at any point?

 

Along with the above advice on firing order, be SURE that the battery is in good condition. Marginal voltage raises heck with engine management. Have it load tested for free at any parts store to be sure.

And yes, you can have a battery that is strong enough to start the engine but marginal enough to give the engine management system fits......

 

Well after working on it tonight it doesn't look good. Yes the distributor was removed, we had to swap the one from the 99 into the 95 block. We have gone over the firing order repeatedly. We narrowed down the miss to cylinders 2 and 3. Replaced the fuel rail and injectors, no change, check spark, all good. The engine had a head gasket done before we got it, so tomorrow were gonna get a compression tester and check that something mechanically is not wrong. I know it ran fine until it was wrecked, so hopefully everything's OK.

 

Make sure that you have that distributor indexed correctly. I can't speak from personal experience, but A LOT of folks have reported very similar problems to yours and corrected that problem by indexing the distributor correctly. (It may need to be slightly different than you'd expect.) Do some research on the XJ dizzy indexing and look at Cruiser's page for detailed instructions on troubleshooting/correcting and see before you go tearing the engine apart.

Edit - Also, don't ignore tjwalker's advice about the marginal battery - it's worth at least confirming that the battery is good. The XJ is picky, it's a lot more sensitive to "less than ideal" battery condition than other vehicles.

 

Well we ran a compression test and the numbers were bad across the board. So off comes the head and it goes to the machine shop. Hopefully its not cracked or majorly warped. This project never seems to end.....

 

Fingers crossed.

I had a Chevy van with a straight 6. The intake manifold and head were an integral casting. One day it overheated and cracked that head. The replacement was more than I cared to pay for so I talked the machine shop into welding it up. They knew a good welder, had it done, got it back and milled it. I installed it and never had a problem.