I acquired a 1989 Cherokee from a friend that has had a 1991 engine put in it, original and donor engines are both 4.0.
It will not run, it is only firing the #3 and #4 cylinders.
I know it is has to do with the engine electronics not matching the vehicle electronics.
Can anyone tell me if I can make this engine work or do I need to find a 1989 engine?

 

There is nothing different between the two engines other than the electronics. The problem lies with the electronics.

What did you swap over into the '89? Almost all of the sensors and wiring are different. If some parts were taken from the '91 that weren't the block or head you'll need to find actual Renix bits.

Assuming of course everything was plugged in correctly.

 

I haven't done anything yet, all parts installed by the previous owner.
He told me he changed the ECM, dist., crank sensor and flex plate.
I was hoping someone on here has seen this before and I could avoid the diagnostic headache.

 

Kinda hard to know what the PO did. Sounds like wrong flexplate maybe. Or wrong CPS.

 

I'm going to look at this thing this weekend.
I hope he put the right flex plate in it.
The way my luck runs it will be the hardest part to change that's wrong.

 

Look to see if the CPS connector has been modified first. The swap can be so simple and people make it complicated.