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98' XJ 4.0 AW4 with 155k on it. An on going issue for the last couple of years. Running rich to the nose yet occasionally throws a running lean code on bank 1. Now it runs rich to the point of spitting droplets of gas out the tail pipe and stalling at stops after it has warmed up. Goes down the freeway fine however.

I replaced the upstream O2 sensor a couple of weeks ago, with no noticeable difference. Looking for ideas on a fix. I have had a couple people guess a bad computer....

With Innova scan tool I get this info

Cold (initial start up)
upstream read .4 - .75
downstream reads .76

Engine at 192
upstream reads 0.00 - .88 (jumping quickly with nothing in between)
downstream reads 1.0 solid (way rich)

STFT remains -4.7 to 0 hot or cold
LTFT remains 6.0 hot or cold

A couple other odd things I noticed. Even when warmed up it remains in CL (closed loop). Shouldn't this have changed to open loop?

Also the TPS reads 15% even at idle. That doesn't make much since, but I have gotten that reading for a couple of years. Is this correct or another source of trouble?
 

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I am not an expert on such by any means. Have a look at this thread here:

http://www.cherokeetalk.com/forum/f23/timing-being-retarded-pcm-wot-43706/

I had/have issues with my PCM's spark advance curve programming.

I would be looking at your Idle Air Temp sensor and you MAP sensor as well. There is some valuable info at the link provided.

I do not believe that there would be a ton of difference between my rig and your rig's PCM programming. Perhaps slightly different in the Transmission control, but most likely very similar.

Good Luck and give us an update when you find out something.
 

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I remember I had a similar situation as you and I had to take my car to my mechanic friend for diagnostics. However, a disaster occurred and all the information about the failures in my car was lost, as it was stored on the hard disk in my on-board computer. I didn't know what to do, but I had to restore my hard drive first. I found some company http://salvagedata.com and I asked for help, everything was certainly not fast, but thank God they helped me and then I was able to take my car with all the information on it for diagnostics. Then I had a repair, for which I had to pay a lot of money, but that's not the main thing. The main thing is that my car is now in order and now I will take care of it more properly.
 
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