Jeep TJ engine bucking

[RJVanna]

Lol, I went for a drive to the local store and I now have a cylinder 3 misfire with lurching again. It's back...

 

[RJVanna]

So here is what I've noticed while driving the car over the last few days of driving. The car runs very rich, I've tracked my mpg and I estimate I'm getting around 8 or 9. The jerking goes away when I restart the car, and I am now getting one code very commonly. P0171 and P0303.

My next course of action is that the computer is thinking the engine is receiving not enough fuel so it's feeding the engine more gas which makes the car stutter. I've unplugged all O2 sensors and ran without them for a while but the lurching still persists.

I'm thinking this could be a map sensor? Does anybody know how often these fail or how to test them?

 

[Link]

Pull the spark plugs and look at them. They will give you an idea if it’s running rich or lean

 

[RJVanna]

So I cut off my 2 cats at the exhaust manifold. One of the cats was empty and the other was definitely clogged up. I read a article that mentioned a 3rd cat. Does anybody know anything about this? I thought it was a resonator because it's before the muffler but now I am having my doubts. Btw 2003 jeep 4.0 if that helps???

 

[Tronner]

Yes there are 3 cats, the only 2 that are monitored on the 03-06 are the two just below the Exhaust manifold. Typically newer Cat kits come with all 3, I would replace all 3 but the third in front of the muffler is not needed so you can remove and just replace with pipe if you so desired.

 

[Link]

I’d replace all three. Unless you need CARB certified cats they aren’t expensive and usually come as a set

 

[RJVanna]

Tbh they don't check emissions here in Arkansas, I'd be lucky if they even checked if I had brake lights lol. I'll fs think about it though. Thanks guys.

 

[Link]

Tbh they don't check emissions here in Arkansas, I'd be lucky if they even checked if I had brake lights lol. I'll fs think about it though. Thanks guys.

We don’t have emissions requirements where I live either. When I bought my Jeep, I could tell the cats weren’t working…and the third cat was missing. The exhaust stunk. I removed the old cats and they were hollowed out. Replaced them and the O2 sensors….and all new muffler and exhaust pipes. It now runs great and doesn’t stink any more.