I have hooked up the battery and it ran just as bad. I unplugged the O2 sensor with the same result however once I plugged it back in it seemed to run a lot better with just a flat spot when reved. I have driven it yet but I am thinking a new O2 sensor might do the trick.
Maybe my approach is antiquated but breaking down under load sounds a lot like a possible ignition/spark issue, when where the plugs/leads last changed?
When I was younger we used to use the problem to help localize the issue, specifically a lead with high resistance will arc out elsewhere and this is readily seen under low light conditions.
Alternatively poor fuel delivery will cause identical problems (as previously mentioned), how old is the pump in the fuel tank? have you run the tank dry recently (rubbish can get into the pump)?
__________________ "Facts do not cease to exist because they are ignored..." - Aldous Huxley
does it backfire ? is the O2 sensor over 100000k old? you might be right
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96 XJ Limited LPG Conversion......
99 XJ Sport ... Finally on the Road
RC Mini Me
If the O2 sensor is really bad, it would usually throw a code. When the computer is re-set the engine will run on its original settings and all should be good. If it starts to run bad again after a while, it may be the O2 sensor.
__________________
Go hard. You can rest when you die
"98 XJ. RE 3.5 inch lift. Dana 44. 4.11's. 32's
Last edited by rustynuts; 12-01-2017 at 08:10 PM.
Reason: typo
Only my personal experience, my 96 had similar problems. I disconnected the battery over night and unplugged the upstream OXY sensor and left it unplugged when I reconnected the battery the following day to ensure the pcm was not using sensor at all. Not sure if you have done this test in this particular order or if it makes a difference?
The xj ran rich, however the symptoms I was experiencing had gone. During this process I found my headers were also cracked which may have been contributing to the problem.
A new set of pacemaker extractors along with a new upstream OXY sensor later saw the xj running better than ever.
How's your battery? I've found these engines hate batteries on their last legs. Very long shot but worth knowing the battery is in top condition and is easy/cheap to rule out.
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1996 Jeep XJ Cherokee
