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I've been a bad boy. Please help.


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Okay the comanche is Dead, I cracked it in two and showed it no mercy once I did. I figured 1.5 years to get it on the road and its gonna break my first time out? Scrap.

 

I did however remain kind of faithful. I bought a 1996 XJ with 4.0L, ax 15, and 231 transfer case, it was purchased for 300 dollars not because of the shape it was in but because of the owner. It had a rough idle when I bought it, so I immeadiately replace the plugs with the correct brand and make and the wires, the cap and the rotor, I even replaced the ignition coil, the feul filter. here's the problem...

 

For the first 3.5 minutes of driving it runs great then when I come to a complete stop and turn a corner it starts bunny hopping like crazy and tries to shake itself apart, however momentarily turning off the engine and restarting it will correct the issue for about 3.5 more minutes. I am stumped as all hell here. The computer says that there is a short in the o2 sensor wiring I checked it, its all good. Even if the O2 sensor is fried, it should still run in dummy mode should it not???

 

Thanks in advance.

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It will run in open loop (without o2) until it times out, or see's that its reached operating temp, I am not sure of which the ECM does in '96. Sounds like a shorted o2. How are you sure the wires are ok? Did you pin out the ECM connector and check for short to ground, short to power, cross short, or open/high resistance?

 

'96 Should be OBD II, and very helpful with a scan tool. I would get my hands on one, and check the o2 sensor outputs in the beginning, and when it occurs. It will also tell you whether it is in closed or open loop.

 

Rob L.

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It might... But I would really suggest getting a scan tool in there, it will tell you a lot. If I were you, and its tossing codes for a "shorted" o2 sensor, I would do a pin out test, find the pins on the ECM, and do a continuity test, to check for opens and high resistance from the ECM to the pigtail (Should be zero to 10 ohms). Then check for any unwanted voltage (with both ends unplugged, anything but zero is bad.) Then check for ground in the harness with both ends unplugged.

 

Rob L.

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