[MrJingles]

Alright guys Im gunna try and explain some stuff hopefully you will be able to follow me... Two weeks ago I began to order stuff for my Jeep after having her for a year with no problems at all. I ordered my lift, tuffy console, and some rear tow points blah blah blah.. Well the first thing that started this was that my check engine light kept coming on but my temp. gauge was running low so I checked the diagnostics and it said O2 sensor not my thermostat which I thought it had to be because of the low running temp. About four days later, I was driving and she started to sputter and sounded like she was gunna die so I slammed the gas and then BOOM! too much raw gas into the exhaust and it blew my muffler up and now it rattles like no bodies business. After that inital sputter it stopped and then later that day it did it again. It has been sputtering on and off since then about 3 days ago. Dad said I might have gotten bad gas so i put some "dry gas" in it and now the sputtering has stopped but I seem to have a lack of power. Could the lack of power be because of the weak back pressure because of my bad muffler? Could a messed up O2 sensor be causing my Jeep to run bad? Also Ive been getting really bad gas mileage are tons seperate things going wrong with my Jeep or is there a way everything can be tied together? SOMEONE HELP PLEASE!

[dadstoy]

Yes, your O2 sensor could and probably is making it run bad. Change it out, replace the muffler and see how it runs. When my sensor was bad, it would run rough, spit and sputter, until the check engine light came on. It did lack power and the fuel mileage went to crap.

[jeepngolf]

Sounds like a clogged cat to me. Probably a result of a bad o2 sensor. Rattling is usually a sign of the cat disintigrating.

[rustywrangler]

with both above. O2 censor needs to be replaced and its time for new exaust. You would not belive the difference I had with just replacing the exuast ( cat and muffler) I had almost no go and after doing that it ran like a champ.

[MrJingles]

Thanks guys but on the way to work tonight it sputtered and was cutting out worse than ever before.. I pulled over and called my dad. turned around and went home and got my moms cars. the whole way home it didnt sputter or cut out but still had a lack of power. Dad took alook at it tonight and said it might be the Electronic Fuel Injection but he doesnt know his way around the technology. Any other thoughts?

[rustywrangler]

OK, sounds like you need to replace what I said above and maybe a fuel filter.

[Vito5800]

I agree with the above posts. Sometimes you can take a small hammer and tap the cat and hear the rattle. I have been in the same situations with other vehicles and it is usually, like stated above, an O2 sensor and the cat. It also wouldn't hurt to replace the fuel filter as well!!!

[Mumachog]

I agree with everyone else. the O2 sensor tells the fuel injection whether you are running rich or lean and how to adjust the mix. if your O2 sensor is bad it can mess up the mix. sounds like you are running rich because of the backfire. like someone else said, a bad O2 sensor making your motor run rich can clog up the cat, but i would'nt worry about the cat unless replacing the sensor soesn't help. an O2 sensor from napa and a flowmaster knock off can prob. be found pretty cheap. fix those first before you drop $ on a cat. i bet if you swap out the sensor it will fix your issues.

[Ramtuff]

check for recalls, some YJ 4cyl had a cat converter recall.

[MrJingles]

Thanks for all the help guys. Didnt have the time to do it myself and I really needed my Jeep back so I took it to the local garage. Bad O2 sensor clogged the cat, the cat gutted itself into my muffler and clogged that. Thats why she was spitting and sputter. New O2 sensor, new muffler and a new tailpipe and 69$ in labor she's running great. I can feel a little lack of power probably because off the now free flowing cat but thats alright. Great diagnosis guys! Thanks for the help again. Installing my RE 2.5" in a week and a half..CANT WAIT!!