HO Motor w/non-HO ECM

[89xjsport]

My '89 Cherokee is getting pretty tired with 245,000 miles. Instead of rebuilding the stocker, I was thinking of looking for a low mileage HO motor to swap in. There's an article at Cherokee America (http://www.off-road.com/jeep/cherokee/99/09_sept/engswap/engswap.html) that describes the swap, but it's kind of vauge. Has anyone here done this swap or could point me to a link for a more descriptive write-up? Also, would there be a cut-off year that I wouldn't want to exceed on the donor motor? And finally, what's the going rate for motors with 40,000 miles or less going for in the boneyards?

Thanks!
Jim

 

[Backdraft]

I bought a 4.0 from my local boneyard that came from a 95 ZJ with around 30K miles. paid about $400 for it. Dude wanted 750, but i can talk pretty slick.

 

[xj4rocks]

what do you want to know? I wrote that article on Cherokee America.

I would imagine that just about any year HO motor that has the distributor (i think they switched to distributorless ignition in 2001?) should work.

 

[89xjsport]

Greetings from a fellow Hokie! We've probably traveled on some of the same trails - I've lived in Pearisburg for the last 11 years. Anyhow, some of my concerns are as follows:

Injectors - does the non-HO harness have to be modified to work with the HO injectors or is it plug and play?

TPS - Can you elaborate a little more on how to get the old TPS to work with the new throttle body?

Vacuum Hoses - does the HO engine have any vacuum related emission or contro switches that tie into ECM function?

Exhaust Downpipe - what's different - does the exhaust exit in a different spot? different size downpipe diameter?

Thanks,
Jim

 

[xj4rocks]

Injectors: The Renix harness plugs right into the HO injectors - no issues here.

TPS: I modified my Renix TPS to fit an unmodified HO Throttle body. Most others have modified teh throttle body to fit the unmodded TPS so that when/if it fails they can just bolt another one on. Most have welded a small tab of metal on to the throttle plate lever. Then use some spacers to space the TPS farther out and bend the tab till it makes contact with the TPS. This allows the unmodded TPS to move as the throttle plate turns.

Vaccum hoses: The Renix system uses an EGR system. This has a solenoid and some vaccum but it doesn't effect anything in the computer if it's unhooked.

Exhaust: Different year exhuast manifolds exit at different angles or different lengths. You can most likely get the correctly downpipe for the year motor you get and it should work.