Totaled 91 XJ

1 Bad F N Z · May 22, 2009

My partner rolled his 1991 XJ. The engine and drive train seems to be okay. If I could find an 87,88,89,90 XJ, with a blown motor, could I pull the motor from the 91 and install it in the older version with the different computer? Any advice would be appreciated. Just like to know what I'm getting into. Thanks

Johnnie Walker · May 22, 2009

FOr the renix era XJ's, you would need to do one of 2 things.. swap intake and sensors. or swap in newer harness and wiring for the HO motor.

89xj · May 22, 2009

to drop in the 91 engine into the 87-90, you use just the 91 block and swap over everything else from the blown 87-90: flexplate/flywheel, intake, exhaust, and all sensors.

there are many diffent ways you can do this swap, search here as it has been done many times. you may want to use the cooling system from the 91.

Slip Kid · May 23, 2009

Swap all sensors and the flywheel or flexplate(required for it to run). Either swap the intake manifold,TB, and injectors, or just swap injectors and adapt the TPS to work with the HO TB. If you need to pass a visual emissions check, you'll want to use the old exhaust and intake manifolds in order to retain the EGR. If you don't have to pass this kind of testing, the best option would be to adapt the TPS, use the HO intake, use the HO header, and ditch the EGR.

I have a 93 motor/trans running on the Renix computers of my 87 XJ. I adapted the TPS and ditched the EGR in order to use the better HO manifold/bigger TB. I retained the aftermarket header I had and welded up the EGR hole, which I suppose could be done with a stock header, but would probably just be added work opposed to using the 91's header.

Injectors are important to swap because I got 11mpg running with the HO fuel injectors, back up to 16 when I intalled the Renix injectors.

89xj · May 25, 2009

Slip Kid said:
Swap all sensors and the flywheel or flexplate(required for it to run). Either swap the intake manifold,TB, and injectors, or just swap injectors and adapt the TPS to work with the HO TB. If you need to pass a visual emissions check, you'll want to use the old exhaust and intake manifolds in order to retain the EGR. If you don't have to pass this kind of testing, the best option would be to adapt the TPS, use the HO intake, use the HO header, and ditch the EGR.

I have a 93 motor/trans running on the Renix computers of my 87 XJ. I adapted the TPS and ditched the EGR in order to use the better HO manifold/bigger TB. I retained the aftermarket header I had and welded up the EGR hole, which I suppose could be done with a stock header, but would probably just be added work opposed to using the 91's header.

Injectors are important to swap because I got 11mpg running with the HO fuel injectors, back up to 16 when I intalled the Renix injectors.

curious, did you notice a difference in performance with the 93 engine compared to the renix? if i ever get around to rebuilding my 89 renix, i was going to use the top end(head, intake, TB, exhaust) from a 91-95. just wondering how much of a difference there is.

Slip Kid · May 27, 2009

curious, did you notice a difference in performance with the 93 engine compared to the renix? if i ever get around to rebuilding my 89 renix, i was going to use the top end(head, intake, TB, exhaust) from a 91-95. just wondering how much of a difference there is.

It is certainly more powerful than the original engine. It's not as great as the 93 engine was in the 93 stock Jeep, but I'd assume that's the tires more than anything. Performance was improved a bit once I finally put the Renix injectors in. But yes, more power, and better throttle response (probably from the TB, which should mean somthin to you) My engine as it is now seems to have a similar powerband to the HO in it's original home, only flattened a bit from my header. I don't recall the differences in the stock exhaust manifolds, as my original one was gone long before I even saw the HO one. But as you're ditching EGR anyway by going with the new intake, I guess is dosn't matter. EGR always seemed dumb to me.. :dunno:

TiRod · May 27, 2009

EGR just mixes exhaust into the intake to lower combustion temps and reduce NOx. The later model cams did the same with a lot of overlap - diluting the intake charge by mixing with exhaust.

Therefore the HO cam isn't the best choice for power as it's actually tuned for emissions. All the other improvements - high port head, manifold changes, throttle body size, etc. had to be done to build back power. Did a good job, too, although it moved the power band up and lost some low end torque.

Slip Kid · May 28, 2009

What are the differences, lift and whatnot, of the HO cam/Renix cam? Or, is the Renix cam better than an HO cam? It interests me, since I still have most of the Renix engine.

Totaled 91 XJ

1 Bad F N Z

NAXJA Forum User

Johnnie Walker

Piece of Fish!

89xj

NAXJA Forum User

Slip Kid

That'll buff right out

89xj

NAXJA Forum User

Slip Kid

That'll buff right out

TiRod

NAXJA Forum User

Slip Kid

That'll buff right out

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