'98 TJ Exhaust: 2.5 cat on 4.0?

[PenultimateLap]

hello. I'm going over my first Jeep and am trying to learn about it. Its a 98 4.0l 5 spd CA Jeep. It passed smog no problem, despite a cracked exhaust manifold, however I am confused on the exhaust and cat setup. Looking at the FSM it looks like it has the 2.5l setup with the small cat in the U in front of the oil pan. It only has a single O2 sensor before the cat. Is this the correct setup? I can't find any info or picture with this setup.

 

[CharlesHS]

The 98 XJ 4.0L that I had which was a CA vehicle had 1 O2 sensor at the inlet to the cat and 1 O2 sensor at the exit of the cat (IF this helps any).

 

[TJ4Jim]

hello. I'm going over my first Jeep and am trying to learn about it. Its a 98 4.0l 5 spd CA Jeep. It passed smog no problem, despite a cracked exhaust manifold, however I am confused on the exhaust and cat setup. Looking at the FSM it looks like it has the 2.5l setup with the small cat in the U in front of the oil pan. It only has a single O2 sensor before the cat. Is this the correct setup? I can't find any info or picture with this setup.

View attachment 192393

Not a 2.5 setup, 2.5's have a large Cat just before the muffler.

 

[HarleyMick]

hello. I'm going over my first Jeep and am trying to learn about it. Its a 98 4.0l 5 spd CA Jeep. It passed smog no problem, despite a cracked exhaust manifold, however I am confused on the exhaust and cat setup. Looking at the FSM it looks like it has the 2.5l setup with the small cat in the U in front of the oil pan. It only has a single O2 sensor before the cat. Is this the correct setup? I can't find any info or picture with this setup.

View attachment 192393

You say you have a cracked exhaust manifold. You can prevent that from happening again by having your exhaust guy put a piece of flex pipe where the exhaust runs parallel to the side of the oil pan on the driver's side.

 

[PenultimateLap]

You say you have a cracked exhaust manifold. You can prevent that from happening again by having your exhaust guy put a piece of flex pipe where the exhaust runs parallel to the side of the oil pan on the driver's side.

thanks guys. it looks like its a shop special setup with a walker universal cat. I had read about the flex pipe which sounds like a good idea no matter what. I still find it weird there is only one O2 sensor, but if it passes smog I cant complain!