Educate me about Renix

[Nikkormat]

Lately I've been working on a 87 Cherokee for a friend. It has 360k miles on the stock drivetrain and it runs amazing but what fascinates me most about it is the Renix fuel injection setup on it.

Compared to the H.O. and later XJ's I've played with it seems to be a very simple system, and it still uses a lot of simple vacuum lines which I love! And the fact that it can self tune each individual cylinder with such simple inputs blows me away. The kid who owns it drives like a freaking maniac, but it still nets him 23 MPG and it has some serious power for being a clapped out old straight six. I'm fascinated, jealous, and amazed at how good it seems to be. When I was researching XJ's 4 or so years ago everyone had nothing but complaints about Renix and that's what really scared me away.

With that being said, I want to hear from some people who have owned and worked on Renix in the long term...

Am I just seeing it through rose colored glasses wanting to hype up the AMC/RENAULT/BENDIX fuel injection system?
What major problems are to be expected from a Renix Cherokee besides the typical CPS failures?
Is his 23+ mpg a fluke or something Renix can accomplish reliably?
Where is the jeezless confuser? I can't find the fargin thing!

[will e]

I have never heard of it. I would be suprised if a FSJ can reliably get 23mpg.

[Tatsadasayago]

The Renix system got a bad rap early on but after almost 30 years many XJs are still chugging along. I think that is vindication of the design.
If I recall correctly, the CPU is hiding behind the passenger side lower dash panel. If you look at the passenger side firewall from under the hood, you can see the wiring harness bulkhead. The ECU is on the other side of it.
In my dealership experience with the 87-90 models CPS and TPS sensors were the common failure parts as well as broken vacuum canisters and plugged cats. The 87-88s also suffered from broken transfer case housings due to front driveshaft compression.
I have an 89 Limited with 158k on the odometer that I actually PDI'd when I worked for Jeep in Reno. A radiator, alternator, starter, water pump, cat and injectors are the only parts I've replaced since I bought it in 91.

And no, 23MPG is not out of the ordinary for these models.

[BCRAWLER]

Have a 90 XJ in the driveway I am about to sell. Has 348k on the meter. Only thing I hated was the cooling system. Hard to burp it after emptying it. Changed out to a 96 rad to get rid of the overflow bottle back by the fire wall. Also put in some switchs to override trans computer. Was able to turn on lockup torque and prevent upshift to 2nd gear for going down really steep hills in the bush. On mine the shifter has 1st and 2nd together.

[tedlovesjeeps71]

Has a lot of vacuum lines that you LOVE?? Dear lord... He's SICK! SICK I tell you!!!
I've owned a couple pre-91xjs and as much as I prefer the Bosch system, they did work. My biggest issues were the seemingly haphazard (messy) layout of everything, the collection of fusible links which were more of a pita than having a PDP. And the overabundance of vacuum lines. As mentioned, the radiator conversion is a big plus since the closed loop design sucked. The other issue I ran into was the pre-91s seemed to get all the junky other components. The Peugeot transmission is a disaster and we all know about the Dana 35 rear. Also, they used the Vac disconnect front 30.
All that said, there is a kid in my school who has an 89 that runs pretty well. He's having a lot of teething issues with stuff like the (horrible) internal slave cylinder, starter, flywheel, etc. If he'd spend some time working on it it would be fine for what he does.
Just remember if you're looking at an Xj, they are getting pretty old for first gens. Rust can be bad. And if it's been wheeled a lot/hard, the unibody can be tweaked causing all sorts of door/rear hatch issues.


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[will e]

Oh, it's an XJ, not an FSJ. I just saw 'cherokee'. My bad.

[Nikkormat]

I'd rather troubleshoot vacuum lines than canbus! Or Chryco electronics for that matter...

[Tatsadasayago]

The Aisin-Warner 4-speed auto in the first gen XJs is a very good unit. They had problems with the shift servos but had that fixed by the end of the 87 model year.
Agreed on the cooling system. The dealership had a special hand pump and tank cap that was used to burp the system. It sucked.

[tedlovesjeeps71]

I'd rather troubleshoot vacuum lines than canbus! Or Chryco electronics for that matter...

You're on your own there brother? 91^ Bosch system is a very good design with minimal issues. Chasing 27+ year old possible vac line issues would drive me nuts. Same with trying to find a bad fusible link in all that spaghetti. I have no doubt you can knock it out of the park but it's not my preferred torture.


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[Nikkormat]

One thing I didn't know was that it was equipped with the peugeot transmission. I assumed it was an ax15. What problems should we look out for with the BA105?

[tedlovesjeeps71]

One thing I didn't know was that it was equipped with the peugeot transmission. I assumed it was an ax15. What problems should we look out for with the BA105?

Run... Screaming from the BA -10! It's a split case design with a left and right half of the transmission held together buy bolts. The least of their issues is the leak horrifically, hence the nickname Puke-goat. They also use an internal slave cylinder which was only marginal at best when new. Slave will leak and fail randomly and requires pulling the t-case to replace. Bleeding it sucks too!

[tedlovesjeeps71]

Also, they may have a 207 T case, 231 maybe. They will also have the earlier 21 spline output instead of the more common 23.


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[Nikkormat]

One thing I didn't know was that it was equipped with the peugeot transmission. I assumed it was an ax15. What problems should we look out for with the BA105?

Run... Screaming from the BA -10! It's a split case design with a left and right half of the transmission held together buy bolts. The least of their issues is the leak horrifically, hence the nickname Puke-goat. They also use an internal slave cylinder which was only marginal at best when new. Slave will leak and fail randomly and requires pulling the t-case to replace. Bleeding it sucks too!

That sounds wonderful! (sarcasm)
Oh well, it works for the time being. I'm assuming an AX15 will swap into it's place with little effort and a matching transfer case?

[tedlovesjeeps71]

One thing I didn't know was that it was equipped with the peugeot transmission. I assumed it was an ax15. What problems should we look out for with the BA105?

Run... Screaming from the BA -10! It's a split case design with a left and right half of the transmission held together buy bolts. The least of their issues is the leak horrifically, hence the nickname Puke-goat. They also use an internal slave cylinder which was only marginal at best when new. Slave will leak and fail randomly and requires pulling the t-case to replace. Bleeding it sucks too!

That sounds wonderful! (sarcasm)
Oh well, it works for the time being. I'm assuming an AX15 will swap into it's place with little effort and a matching transfer case?

Yup. That's the saving grace. All the newer tranny/T cases will bolt up. If you need a 231 let me know. I have an extra. Or you could do a dana300 flipped.


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[derf]

One thing I didn't know was that it was equipped with the peugeot transmission. I assumed it was an ax15. What problems should we look out for with the BA105?

The Peugeot transmission was once described as being like having a grenade with the pin pulled. It was just a matter of time before it explodes.

Fortunately, if you grab an AX15/231 or NV3550/231 combo out of an XJ or Wrangler (YJ/TJ) it's easy to do the swap.

[letank]

there is a special post about renix on naxja.org. A bit of a pain to debug, I had a wrangler with the renix and the 5 speed... fortunately my daughter forgot to monitor the coolant temp, so the head and the block cracked... so I did not have to service it anymore, but honestly at 198Kmiles it did not even burn oil between oil changes.. mostly rechecked ground, CPS... the BA105 is known for its weakness.

and there is a yahoo group where some people from an eastern country started to poke into the cpu and gave the program away... but who wants to download stuff from the eastern side...?

Post edit Oct 2019, in case somebody decides to query for Renix, I found these sites

http://cruiser54.com

and somebody doing gizmos from data to multiple fan controller

https://nickintimedesign.com/shop/

[Stuka]

Owned an '87 XJ Limited with a Renix 4.0, I liked it once I learned it. It has a few quirks, but is not a bad system by any means. That thing had 180k on it, ran good, aced emissions, no complaints. I did have to work on it, adjust the TPS, replace the IAC, etc. But was nothing overly hard. My ONLY complaint on that Jeep was the POS Bendix ABS. That stuff was a deathwish.

[Tatsadasayago]

Owned an '87 XJ Limited with a Renix 4.0, I liked it once I learned it. It has a few quirks, but is not a bad system by any means. That thing had 180k on it, ran good, aced emissions, no complaints. I did have to work on it, adjust the TPS, replace the IAC, etc. But was nothing overly hard. My ONLY complaint on that Jeep was the POS Bendix ABS. That stuff was a deathwish.

No kidding re; the ABS...

I used to take brand new XJs from the dealership in Reno and go up to Mount Baldy, on the north end of town. Going down that hardpacked 45 degree+ face, I'd hit the brakes and that damn ABS system would start pumping and the speed actually increased. I learned real quick that it was best to stomp the brakes, put the trans in reverse and hammer it in order to stop before hitting the bottom of that 2000'+ face.
Yup total garbage.

[Grand_Wag_85]

I had a '90 Cherokee Pioneer with the Renix, no complaints here. Not sure why everybody hates on them so much. 200,000 miles, awesome fuel mileage and dead reliable. Actually used the XJ to tow FSJ's!

One thing I will say about the manual transmission Renix XJ/MJ's....When the clutch MC goes out it will piss brake fluid down the fuse block. They moved the fuse block with the HO Jeeps.

Which reminds me the '90 I owned had an internal slave cylinder AX15.

[BCRAWLER]

My ABS system quit working and I replaced it with a simple master cylinder and was happy with the change