My son and I are building a 91 Cherokee. We just swapped a 94 I6 HO into a 91 .... it starts and idles fine, runs smooth to 2500 RPM even under load. Then begins to miss and barely rev to 3000. New exhaust incl. CAT, new dist cap and Rotor, new plugs. Swapped: plug wires, Injector rail and injectors, throttle body, coil, computer (these all came from some doner cherokees we have for parts) The 94 was coupled to a manual but we are using the auto from the 91 so we are using the 91 flywheel and 91 crank sensor. I really need to get this running for my son .... HELP I'm going nuts.

EJ :(

 

have you put the 91 throttle body on the 94 ?

sounds like a tps trouble....in 94 the pins in the connector where differnt then in 91

id try this first ...no reason except a elctronic signal that could cause this

Ive put a 99 4.0L in my carburated 86 (harness modifiedto fit) without any problems ,so!


you changed the whole exhaust , hope you kept the O2 sensor ....

 

Thanks for the reply ...
My son and his buddies had originally bolted the 91 Intake manifold to the 94 block. We intalled the motor and it fired but we ran into the 'no revs' issue. So when they told me what they did... I got the guys to swap all the 91 parts back to the 94 parts (injector rail with injectors,Throttle body, ECU) but the problem is still there. Since we still have the 91 TB connectors (91 wiring harness)... maybe that could be an issue. Or maybe the TPS is just bad?
I'll take a closer look at the TPS ...Thanks again. I'll report back ...

EJ

 

Sorry about the delay ... but I should get back with the solution to the issue. Ends up the Crankshaft position sensor was loose. We tighted it up (we actually put the correct bolts in place) and it works great ....
EJ

 

glad to hear that you solved the problem ....finaly !

 

I didn't ever see your posts... if i had i could have saved a bunch of time...

i had the same symptoms and solution with my 89 -93 4.0L Cherokee swap... but never saw your post.

at least its up and running smooth!

 

sounds like either tps or mass air sensor