I have a 1987 XJ with the 4.0. It was running fine until one day it wouldn't start. The CPS tested bad so I replaced it. I found an issue with the distributor cap and replaced the cap, rotor, plugs and wires. After that it would start, run rough for a few seconds and die. I have tested the new CPS and bypassed the CPS connector. I have cleaned the dipstick ground and replaced the chassis ground. I have tested the CTS and MAT. I have swapped out the TPS, IAC, MAP, and Coil/ICM. All the vacuum hoses appear good and I don't hear any leaks. The fuel pressure tested within specs. All this lead me to the ECU. I borrowed an ECU from a 1990 XJ with odd results. With the "new" ECU she fired up and idled nicely, but sputtered when I gave her gas. So I put the "old" ECU in the 1990 and it ran normal. Put the "old" ECU back in my Jeep and it went back to idling like shit. I thoroughly cleaned the C101 connector on the firewall and the ECU connectors under the dash with no change. I have no idea what to do with this thing :dunno:
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starts, sputters, dies...
- Thread starter tazam80
- Start date
Alaskan89XJ
NAXJA Forum User
- Location
- Alaska
Not sure of the ECU issue you tried with the swap. Seems I recall that there are different model numbers, (I have not the various numbers available at this time). However there is an internal forum discussion I found by googling: renix ecu numbers. 
member has a title, there, called: "Anybody have cross reference for numbers on Renix ECU's?" For some reason I can't figure out how to link that page to this one. Hmmm.., anyway it would seem the '90 model Renix ecu might give you certain enhancements over the older one you have. That said, I am one who prefers exact replacement models until proven otherwise. If you go to that page's discussion you will see at the bottom, a list of the proper models for those Renix years, and the different transmissions.
member has a title, there, called: "Anybody have cross reference for numbers on Renix ECU's?" For some reason I can't figure out how to link that page to this one. Hmmm.., anyway it would seem the '90 model Renix ecu might give you certain enhancements over the older one you have. That said, I am one who prefers exact replacement models until proven otherwise. If you go to that page's discussion you will see at the bottom, a list of the proper models for those Renix years, and the different transmissions.looks like there are 2 ECU options...the one I have and the one he has...everywhere I have looked says the later year is better, but I'm still not sure if the ECU is the problem.
I'm going to re-adjust the TPS and recheck the CTS and MAT...I'll repost if that leads anywhere.
I'm going to re-adjust the TPS and recheck the CTS and MAT...I'll repost if that leads anywhere.
joe_peters
NAXJA Forum User
- Location
- Grants Pass, OryGun
Late to the party!
Any updates?
Any updates?