1990 4.0

Gabriel Villescas · #1 (**permalink**) 10-10-2007, 09:31 AM

Hi my name is Gabriel Villescas and I have a jeep question. My father has a 1990 jeep truck with an in line six cylinder 4.0L. He had the engine rebuilt at a local machine shop/mechanic and they messed it up a number of times and finally on the third time they forgot the ground and went to test start it and it grounded through the throttle, welded it wide open and blew the engine. Well, they found a donor Comanche with a newer engine and put it in. The truck will not run well. It stalls, misses and wont pass an emissions test. The casting codes for the engine in the vehicle now revels that it is for a 1991-1995. Is this compatible with the computer and other various components and electronics in the 1990? thanks for any help you can offer.

tardis454 · #2 (**permalink**) 12-02-2007, 03:29 PM

The 1990-down L.O. 4.0L's (87-90) use a different cylinder head/intake, and ECM than the 91-up HO 4.0L's. 91-up 4.0L intakes have raised intake runners. Depending on what head/intake you are using will determine what your next step is. I've seen H.O. motors use L.O. intakes/ECM's successfully...Need more info and pic's from your end...

Bounty__Hunter · #3 (**permalink**) 12-03-2007, 03:17 AM

The later engine can be used, as long as they reused the '90 intake, throttle body, and sensors.

Sounds like it is time to cut your losses and take it to a reputable shop.