I have an 87 Cherokee that has a 91 H.O. motor in it but still retains the original 1987 efi set up. I also have a 94 cherokee for parts that the block and head is being donated to my wifes worn out 92. So I was thinking about swapping the fuel injection setup into my 87. Does anyone know if it would be too much trouble to convert to the newer MPI setup from the 94 cherokee?

 

I suspect the HO engine with ’87 fuel injection will run lean. Fuel maps that use a MAP sensor rely on known flow to provide correct fuel delivery. The MAP sensor only measures pressure. So if the HO engine flows more air than your non-HO, at a given pressure the stock fuel delivery would be inadequate.

Personally I’d start by installing a wide-band air/fuel sensor and gauge and playing with the fuel pressure and/or fuel injectors.

I only have the Chilton manual and unfortunately it doesn’t have the ECM pinouts. If you can find this info somewhere you could tell at a glance if it’s plug and play or if you’ll have to swap the entire harness and sensors.

 

Do a search on the HO renix hybrid write up I did in the write up section... your intake and exhaust porting isn't lined up now... I had a 89 with a 96 motor... so I created the hybrid to make it all work properly...