Computer issue?

[1990JEEPXJ]

So as my screen name suggests I have 1990 XJ 4.0 auto and have been recently dealing with a intermittent rough idle. I narrowed it down to the #2 injector not getting a signal. And when I say it’s intermittent, I mean it depends on how the Jeep starts. If the Jeep’s starts and is running on all 6, it won’t start missing or running rough. But if I start it and is missing, it won’t correct itself. Because it’s dependent on ignition cycle per se, that leads me to believe it’s a computer issue. The lack of signal was confirmed by an injector test light.

I have read injector issues are commonly computer related for the renix Jeep’s. And because it’s not a random miss makes me think it’s not an actual wiring issue.

Injectors are new as well as the fuel pump, filter, cap, rotor, wires and plugs. When it runs good it’s runs good. It passed smog on a cycle that it was running good on. Lol.


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[lawsoncl]

So as my screen name suggests I have 1990 XJ 4.0 auto and have been recently dealing with a intermittent rough idle. I narrowed it down to the #2 injector not getting a signal. And when I say it’s intermittent, I mean it depends on how the Jeep starts. If the Jeep’s starts and is running on all 6, it won’t start missing or running rough. But if I start it and is missing, it won’t correct itself. Because it’s dependent on ignition cycle per se, that leads me to believe it’s a computer issue. The lack of signal was confirmed by an injector test light.

I have read injector issues are commonly computer related for the renix Jeep’s. And because it’s not a random miss makes me think it’s not ac actual wiring issue.

Injectors are new as well as the fuel pump, filter, cap, rotor, wires and plugs. When it runs good it’s runs good. It passed smog on a cycle that it was running good on. Lol.


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Inspect the wiring along the fuel rail and where is crosses over from the engine block to the firewall. It's common to have the wiring there damaged from excessive flexing or chaffing, especially if you have bad motor mounts. Shake, wiggle, and flex it to see if it affects anything. You might need to unwrap the loom to see everything. I would believe a bad injector, connector at the injector, a bad crimp connection in the harness, or wiring to the computer before I'd believe an intermittent computer problem. Usually if it's the computer, it's a blown injector driver from a short in the wiring or the injector and it stays dead.

 

[cruiser54]

This^^^^