First time CF user. I currently have an 87 XJ wagoneer/cherokee. It runs absolutely perfect for the most part. I don't even have the common high idle. It has 430k miles and runs strong like my 99 XJ. My issue is I can't go wot without frying the ecu. The ckp, dist, ICM, plugs, wires, cap and rotor are all new. I'm thinking it may be a tps issue, but would like to get some feedback from the experienced renix members. The wiring harness is almost perfectly stock except where three of the tps wires have been bypassed from the C101 connector. I've now fried 3 ECU's trying to figure this out. Any help would be appreciated greatly. Last thing. I have two cut wires towards the rear of the harness right behind the number 6 injector wiring. No clue what they were supposed to go to. Again I greatly appreciate any info.

 

I recommend reading through Cruiser54's Mostly Renix Tips in the Write-ups section while you're waiting for someone to respond.

 

If the two cut wires behind #6 injector are white with blue stripe and violet then the factory ckp (cps) wires were run straight to the ecm (bypassing the C101 connector). I think you are on the right path in thinking you have an issue with the tps. Let's see what the renix vets have to say.

 

If it were my Jeep, I would do the following:

1,3,5, and 27 in my link below.

 

I read cruiser's info. This did not help. I do not see a link. The ckp sensor wire goes through the firewall and straight to the ecu. The confusing part was the second ckp sensor wires going through the firewall a couple inches away. When I checked that connector it was disconnected from the ecu under the dash. Its acting as a plug for a hole so that isn't an issue. I don't know what color the two cut wires behind the number 6 injector are. Its raining today so I'll try to degrease them tomorrow. I found another tps in the glove box. I figured I would check resistances of both sensors at wot and see if there is a difference. I also know at wot the fuel pump switches from the fuel pump relay to the o2 heater relay. I'm thinking that could be an issue as well. Too many places to look at once. Figured some renix vets have some input. My local renix guys have not ever seen a renix fry an ecu.

 

Apologies for the last comment. These two wires are not cut. They go straight through the fire wall. Knock sensor maybe?

 

Again, more apologies. Still getting used to the forum thing. I don't see a link.

Got it. Can't see it on mobile.

 

There was a bulletin to do a CPS patch harness. Perhaps the dopey tech didn't cut off the old plug? Seen it before.

Is your CPS wire harness routed properly?

You can see my link here, right?
https://www.cherokeeforum.com/f51/cr...x-tips-153657/

 

Probably didn't remove old ckp wiring. As mentioned before its only plugging a hole in the firewall. Ckp works fine. Just put it in two weeks ago and it ran fine. The engine just stops altogether when I try wot. The ecu fried. 3rd one now.

 

What's "fried" and what are the symptoms?

 

Ecu is fried. Symptoms are no fuel pump and no spark. I only know how the ecu is fried not why. I've fried 3 ECUs. The waggy runs perfect after I replace the ecu. Only when I try wot does the ecu fry.

 

Sounds like a hot lead short...?
If it is your ECU frying, take a look at the pins in locations for burn or heat(might have to pop open the box):
1,2,10 grounds
13,16,31 hot leads TPS and MAP
and 28 CPS
may give you a lead who knows?

 

It might be something else. That's a tough purer.

It might be something else. That's a tough purer.

Just from wrenchen for allot of years, I can say if it's goofy and makes no scene, check the grounds. The Renix ECU may be "aviation" grade.

Note that all the sensors ground through the ECU. My guess is it's set up that way to protect the sensors from shock from the ground side.I assume you have cleaned your ECU,tcu ect grounds at the dipstick, and have an (one) ohm "ish" resistance in your ground circuit?

Jeepher, if you could state your current problem, that would help.

AND: (A"blind" guess would be a wiring harness issue. Like the 12V feed to the 02 sensor, blowing back into the 5v ecu output) Something like that. Don't forget a hot wire in the harness will cut right through the insulation to the others)

 

Just WOT?? All I know for sure is that cuts off power to the injectors. That bypasses all, goes to default with the exception of no injector pulse.

I took just a second in the FSM. Don't see anything that open loop would blow an ECU. If indeed the ECU's are failing, it's got to be the harness.

AGAIN, what are the problem symptoms?

 

If you need another ecm, I have one on the shelf. Send me a private message and I'll give you a fair deal.