So here's the thing. My '96 has been giving me a lot of trouble lately with bad smelling exhaust, loss of power, and terrible gas mileage. I replaced O2 sensors and spark plugs and put on a new catalytic converter (my old one got plugged up) and my computer is still giving me 3 O2 sensor related codes. It says they're detecting lean and rich mixture, and the sensor itself or wiring may be faulty. So after nothing I did worked I noticed an unrelated fault in my rear suspension. A leaf spring center pin broke and shifted the thrust angle of the axle. Since I could see a visible problem and I knew how to fix it, I decided to tackle this instead of figuring out the gas mileage. Well, after I fixed the axle, the gas mileage problem went away. My Jeep ran good and didn't smell bad at all either. I decided not to question how on earth fixing the rear suspension could possibly change the fuel mixture because it was working and thats all that I cared about. It was this way for about a month and I went in a disconnected my battery and reset the computer to see if the check engine light would turn off and now the old problem is back again. Terrible gas mileage, bad smelling exhaust, low power, and the occasional misfire. I have never heard of anything like this happening before so I'm completely stumped. I just wanna get it fixed before my engine destroys itself completely. Any suggestions as to what might be causing this would be greatly appreciated. Thanks.

 

Replace all normal tune-up items. Plugs, wires, rotor, cap, air filter, etc. Timing is set at the factory, but your #1 terminal should be at 5 o'clock.

 

I just went through a similar situation with O2 and misfires. Granted I have 3 cats and 4 O2 sensors, it was a beast to figure out. After nearly $1200 in shop costs and parts, I would recommend two things

Run only OEM NTK sensors

Get your jeep on a nice scanner that reads LIVE data.

This is what eventually led to me finding that I had an intermittent signal failure from one of my O2 sensors. I ran a new wire from the sensor to the computer and all has been well since.
Not suggesting this is your problem, but being able to watch the signals from your sensors is invaluable in the diagnosis process.

Hope you get it figured out

 

I had 2 NTK sensors that were bad right out of the box. Chased the light, took a while to find them out. They were the last things I expected. Cost me extra money and time.

I've never had a problem with Bosch.

Go figure.

 

That's terrible. None the less, in functioning form, the NTK sensors will communicate with the computer better than Bosch. At least that's the general consensus of this forum and the dealerships.

 

NTK is the OEM for Jeep O2 sensors, but whenever possible I choose Denso over all else. Just my 2 cents

Your bad mileage problem is most likely an O2 sensor issue. When you disconnected your battery it probably reset your fuel trims

 

Sorry I haven't been on in awhile to answer these. Working two jobs has its disadvantages haha. Thanks for the input, I think this is a great idea. I'm hoping to get this thing fixed for real this time, I'm dying to go exploring again!

 

I don't know enough about Jeeps to tell you if this is the problem, but many older vehicles have a jumper you can disconnect to reset the timing, if you feel that that is your issue. The Ranger I used to own had a low power/rough idle issue and disconnecting that jumper, setting the time, and reconnecting it solved the problem. This was a time before OBD so it may not be relevant to your vehicle. It sounds to me that you're gonna need to track down a faulty O2 sensor, but checking the timing might do something. Maybe. I doubt it, but if you have a light and I'm correct then it may save you some time. Again, I'm new to jeeps and trying to apply old knowledge.

 

At any rate a multimeter rental may be a sound investment if you know how to work one.