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92 XJ ECM in 93 ZJ?

Overland

NAXJA Forum User
Looks similar enough, both 4.0 engines. It has a lot of slack in the distributor shaft but I feel like it should still run, even if poorly. Truck belongs to a neighbor who picked it up with fresh ignition components including cam position sensor. Looking at the coil wire, it throws spark intermittently. I sprayed a bunch of carb cleaner in the intake to start with, but the engine doesn't fire at all.

"They said" they could wiggle the computer connections and it would start, but he's never heard it run. I'm thinking cam sensor interface, ECM ground circuit, or the ECM itself. I have a 92 XJ not doing anything that I could cob the computer out of, do you think it'll work?
 
It will start and run for engine diagnostics but it may not be able to talk to the ZJ BCM (do 93 ZJs have a BCM?) and it won't run a 4xRE transmission. If the ZJ has a 4xRH series transmission, it should be fine.

If the ZJ has an OHC or the fancy status screen in the middle it might not talk to that either. Not really sure.

edit: ECUs very rarely fail in these... though OBD1 SBEC ECUs are becoming more common failures and have been for 5 or so years. Typical failure mode is the ECU being completely dead or only running rough, and if you turn the key to on without starting the engine you may hear a high pitched buzzing or squealing from the ECU. If you hear this, usually replacing 3 or 4 capacitors on the PCB and re-potting the reworked areas with non-acid-cure RTV silicone will restore it to full function. When they have failed like this they often won't even blink the CEL at key-on.
 
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