Smell going uphill

[MrBClark]

Could smell that be gasoline fumes? My thought is there's a bad upstream O2 sensor causing the air fuel mixture to have gone full rich.

If you replace them make sure you only install NTK and definitely not Bosch.

So does it sound like the symptoms of a bad upstream 02 sensor? It seems to run very rich and lately, it's even if I give it a little extra gas. It seems to only do this when warm. As a side note (this could just be me losing my mind) but it seems to feel kinda low on power when its been running for a while. I may just replace both upstream sensors anyway cause I don't want to ruin my new cats

 

[Jerry Bransford]

That does sound upstream O2 sensor related. If you replace them make sure you kmly install NTK or NGK branded sensors. No Bosch or store brands.

 

[MrBClark]

Rarely, the computer has a difficult time knowing when an O2 sensor is lying or telling the truth. My TJ came with random O2 error codes and misfires but the previous owner already tried unsuccessfully to fix them with all new NTK O2 sensors which didn't fix it. The O2 sensor codes were ultimately cured by replacing the cats. That just illustrates the computer is pretty weak at figuring out what's wrong in the air/fuel ratio area.

I'm thinking the aroma you're smelling is fuel which is a classic symptom of a full-rich mixture... a classic symptom of a bad O2 sensor erroneously and continually telling the computer the ratio is too lean. The computer keeps richening the mixture to no avail until the fuel mixture is as rich as it can make it.

Replaced all the upstream sensors with new NTK sensors. Still makes the awful smell. Now what? How would I go about looking for vacuum leaks? What about a bad temp sensor? This Jeep really doesn't like me...

 

[TJ4Jim]

Just wondering, what was the condition of the old cats when removed, where they just basically plugged or did they break up.

 

[MrBClark]

Just wondering, what was the condition of the old cats when removed, where they just basically plugged or did they break up.

There was a code for a bad cat. I changed the downstream sensors and reset the codes. It came back everytime. The smell began to get much worse (before I changed the cats). I read where that smell is often a bad cat, and given the fact the I had a code for a bad cat, I decided to change all 3 converters. Now the smell is worse then ever I feel.... all O2 sensors were changed and all the cats are brand new. Actually there is 1 downstream sensor that I am unsure if I changed it. No codes tho...

 

[TJ4Jim]

There was a code for a bad cat. I changed the downstream sensors and reset the codes. It came back everytime. The smell began to get much worse (before I changed the cats). I read where that smell is often a bad cat, and given the fact the I had a code for a bad cat, I decided to change all 3 converters. Now the smell is worse then ever I feel.... all O2 sensors were changed and all the cats are brand new. Actually there is 1 downstream sensor that I am unsure if I changed it. No codes tho...

Do you know the actual condition of the converter media inside of the old cats. I'm asking because if the media disintegrated and found its way into the muffler that can create a back pressure issue.

 

[MrBClark]

Do you know the actual condition of the converter media inside of the old cats.

Looked better then I expected tbh... not that bad really.

 

[TJ4Jim]

Looked better then I expected tbh... not that bad really.

Condition of the remaining exhaust piping and muffler all good.

 

[MrBClark]

Condition of the remaining exhaust piping and muffler all good.

Well the rest of the exhaust was replaced with a new MBRP cat-back last year. It has black soot in the exhaust tip but nothing that alarmed me. Tomorrow I plan on replacing the air filter. Could it possibly be the temp sensor? The gauge on my dash works fine but maybe I'm missing something?

 

[TJ4Jim]

Well the rest of the exhaust was replaced with a new MBRP cat-back last year. It has black soot in the exhaust tip but nothing that alarmed me. Tomorrow I plan on replacing the air filter. Could it possibly be the temp sensor? The gauge on my dash works fine but maybe I'm missing something?

Ok, I was thinking some form of back pressure but it sounds like you have it covered.

 

[Goatman]

You could have shit inside the muffler from a cat. That could cause the smell.
Also, and only because it happened to me, though it sounds impossible, I had a mouse nest in the air filter of a different vehicle. Started it up after it had sat for a few weeks. Ran poorly, figured it was from sitting and the damp weather we were having. Then I started smelling some real odd smells. Turned out the mouse nest had somehow been sucked into the throttle body, and at least some went in the engine, through the intake and exhaust valves (??) and got logged in front of the first catalytic. After digging as much crap out of the pipes as I could it slowly seemed to burn through whatever I had missed. I know this is a long shot, but have you dropped your muffler (though i think you have basically a straight pipe muffler) and checked for any debris?

 

[MrBClark]

I didnt notice notice anything strange when I replaced the rear most cat that connects to the muffler. Maybe though. I'm thinking either a cracked exhaust manifold, bad air filter, or a vacuum leak is causing this issue. I kinda doubt it can be an exhaust leak cause I dont hear it, but when I start it cold, I can hear a faint ticking. I have the 2 piece manifold tho so I'm not sure. And that mouse going through basically your entire system is crazy. Can't believe it went through your engine with any issues.