Losing power and backfiring

[Smasek]

My jeep was running rough, losing power and just acting like there was no fuel being delivered at all. I had a check engine light on and it was throwing o2 sensor codes. I replaced them with NTK sensors and it ran fine today until I was on my way home. While shifting from 2nd to 3rd it started to do it again so I downshifted to 2nd and it went away and drove fine the rest of the way home. I have perfect fuel pressure no vacuum leaks and I have a heat shield over my number 3 injector along with a fairly new camshaft position sensor so I don't understand what's going on. I don't want to end up dumping money into the wrong parts so please help me figure this out.

 

[billiebob]

The losing power sounds like a plugged cat.... but the other symptoms indicate more.
Amazingly there is no code for a plugged cat.

 

[Smasek]

The losing power sounds like a plugged cat.... but the other symptoms indicate more.
Amazingly there is no code for a plugged cat.

I live in Florida so they are pretty lenient as far as exhaust laws go. Should I just hollow it out or even eliminate it all together? I've already put a good bit of money in it so I don't really want to drop the cash on a new cat.

 

[Goatman]

Replace any emissions that need it. Just hollowing out the cat doesn't really fix the problem. The computer is designed to give you the best efficiency. Bypassing o2 or cats just pumps more pollution in the air for no good reason. It's not like in the 70s and 80s where there were 3 miles of vacuum lines and idiot sensors. Fix it right and keep it right.

 

[Steel City 06]

I ran through a similar issue recently. I had multiple random misfires to the point the engine went into limp mode, and I couldn’t rev above 2200 rpm or run significant throttle. Tried replacing everything with no success.

Eventually, I pulled the cats to find one of the pre-cats self gutted and plugged the 3rd cat. A new set of Magnaflow cats and I am back up and running.

Check your catalysts when you get a chance. Buy or borrow a cheap borescope and peek in the oxygen sensor holes to see if the catalyst is damaged, plugged, or missing

 

[Smasek]

Ok. So will it be ok to buy one of the universal cats they sell at pep boys or auto zone?

 

[Steel City 06]

Depends upon state inspection requirements (I suspect they’re fine in FL) and your installation skill. Many require welding to install.

I chose to buy the Magnaflow assembly because it was pre-welded and 100% bolt in. It’s not as cheap as other options, but it saved me a lot of time, and I didn’t have to pay a welder (I don’t currently own a welder).

Be sure to check your cats before you buy new ones. They’re not cheap, and replacing them when you don’t need them is a waste of money. If you’re lucky, it could be as simple as a bad camshaft sensor.

What specific codes do you have?

 

[Smasek]

I only have the one cat on my jeep and I work in a metal fabrication shop so I'll weld it. The codes were for the 2 o2 sensors I have and I replaced both and the engine light has not come back on so there's currently no codes. The cat is rusty and probably original to the jeep so its probably safe to say it needs replacing either way.

 

[Goatman]

A cat can (and theoretically should) last the life of the vehicle. So if you have an old cat that still looks good inside then I would leave it be.