92 XJ ECU connector

[marc davis]

I have a 92 XJ with about 250k miles. Auto, 4wd, 4.0L. The engine has been shutting off at random. At first I shot gunned ALL the sensors, checked all the grounds replaced the distributor, ... Pretty much everything everything I could find in any thread talking about this type of issue. It was hard to diagnose because it will usually start running again in a few minutes, before I can get out tools and a scanner. Finally one day it failed long enough to get a scanner hooked up (old Snap-on unit for OBD1). I got no connection to the ECU. Interesting. I started wiggling wires around the engine bay and finally moved the wire bundle at the ECU. The ECU came to life. Since then I have "fixed" the stalled engine several times by moving the wires at the ECU. I removed the plug from the ECU and cleaned the pins of the connector. I also found that a pipe cleaner would fit nicely inside the pin holes of loom connector and cleaned each pin. I applied some dielectric grease and put it all back together. The issue went way for about 5 months. Now it's back and the same "fix" works. Wiggle the wires and the check engine light comes back and the engine start right up. At this point I'm looking for a more permanent solution. I can try cleaning the connector again. Perhaps hit it with some connector cleaner and scrub the pins, but I suspect that will only buy me a bit of time. I'm looking for other ideas. Replacing the harness with another used one seem like trading one batch of issues with another. I could replace the ECU and hope it helped. I've thought about hacking off the end of the harness and installing a different type of connector, then soldering wires to the pins of the ECU and terminating them in the same new connector. Kind of extreme. But, clearly I'm willing to go to extremes to keep this thing running since I've put this much effort into it already. Another thought or ideas?

 

[Rob Mayercik]

I had a similar issue many years ago with my '92, only in my case it was the "bulkhead" connector at the firewall (where the enging bay harness mates up to the under-dash fuse block and cabin/body harness and I was experiencing total, vehicle-wide blackouts. I was able for a while to get by with wiggling the wires, but I ultimately hacked the connector (and about a foot of harness out of a "Cash for Clunkers" 93 at a junkyard so I could do a full connector replacement.

When I started in on that, I found some of the wires had completely corroded away, most notably the 10-gauge one in the center. It was still "laying" agaisnt the pin and making contact, but as soon as it shifted it could black out the truck.

You might want to check to make sure the wires are firmly connected to the backs of the pins in the connector, and not corroded. Might be worth looking for a connector in good shape at the junkyard and snatching it up to replace your own (I did mine by doing one wire at a time with heat-shrink splices, then I packed the rear of my connector with dielectric grease.

 

[marc davis]

Thanks Rob
I wonder how common a failure the ECU connector is. I'm betting that the majority of bad ECU are actually bad connectors that start working again when the connector is reseating to he "new" ECU.

 

[cruiser54]

RCBRC

Refresh Connections Before Replacing Components.

 

[PacificEd]

I will have to check this out. My 94 would just shut off for no reason while idling or driving. I replaced all the logical stuff (except the distributor) and I finally gave up.

 

[Rob Mayercik]

Thanks Rob
I wonder how common a failure the ECU connector is. I'm betting that the majority of bad ECU are actually bad connectors that start working again when the connector is reseating to he "new" ECU.

I'm not sure - I'm still on my original ECU connector myself, though I did have to replace the ECU about 10-12 years back (it died after getting wet once off-road, think the "potting material" failed down and let water/mud get to the actual circuitry).