alright so i have a 97 xj that i got about 3 weeks ago. It has 195000 on it. So it does this weird thing. When im cruising along the rpms drop. if you floor it it pulls out just fine. It only does this when its been idling or just started. Now the guy before me hacked the cat out. I have a check engine light on and it says a misfire and o2 sensors. So ive changed the plugs and the wires are in perfect shape. There actually 7mm edge pros. I also ran injector cleaner through. So is this an o2 sensor issue or fuel pump. If its an o2 sensor will replacing it work? I dont want to spend the money to replace it if it just keeps going bad!
Also I asked this under the ask the question thread and there were no answers. so thats why i started a thread

 

Replace the upstream o2 sensor and put a cat back on.

 

X2

 

Does it have a downstream O2S at all? Your PCM will be looking for two O2S's and if it can't find the downstream O2S it will get pissed and put the CEL on.

You should always check the O2S heater fuse in the PDC first when there's a O2S related CEL.

If you look in the PDC, facing the firewall, the O2S heaters fuse is a 15 Amp fuse in the top row of mini fuses, second in from your left.

I'd post a pic of it but it takes forever to fire up my Photobucket. I'll do it after I finish this six pack of beer.

 

Here's a pic of the PDC showing the location of the O2S heaters fuse.