Couldn't really find anything in regards to my issue so, Looking for some advice / tips. I swapped a 97 engine into my 2001 xj and decided to weld a bung to accommodate the second upstream o2 sensor. Welded the bung maybe about 2½ inches away from the original o2 sensor location. The downstream ones aren't connected because there is no cat... The car runs like **** but when I disconnect both upstream o2 sensors, the pcm goes into some sort of default mapping and the car seems to run fine, although I know for a fact it's running rich. Does anyone know about a solution for this? I'm not trying to dump all that fuel into the cylinders....

 

Take a picture of your upstream sensor placement. If you have live data of your fuel trims that would be helpful.

 

I suspect you'll need to run the dual-outlet exhaust manifold so that each O2 sensor only reads the appropriate bank of of cylinders, versus both sensors reading all of them. Assuming I'm interpreting your description correctly...

 

I ended up buying the adapter plate in order to use the newer exhaust manifolds on the older model 4.0's. I could have had someone mix the issue at a tune shop but they wanted to charge 400-650.... I should of done this from the beginning.

 

Yessir, I bought an adapter plate in order to use the original manifolds the car came with. Now we play the waiting game. It should run perfect now. I really liked the catless sound but at least I won't have to deal with the smell anymore.

 

The federal emissions version of the 00 dual outlet setup doesn't have cats in the downpipe, only the single one right before the muffler. Using that in my 88...

 

You can go that route, not my first choice. The 01 Exhaust manifold sucks almost as bad as the 0331 head. I put a 98 in my 01. I had a muffler shop weld a bung into each exhaust collector right before they join into the main... so o2 sensor 1 reads 123 and o2 sensor 2 reads 456...I have no primary cat per se...I run the stock 98 manifold and it runs into my "resonator"...which I think is a cat...then I had a pipe with 2 bungs installed between the resonator and the muffler which now houses my 2 downstream o2 sensor...in the same pipe. Have never thrown an o2 sensor code, upstream or downstream. What did you do about ignition...I did not think the coil rail connector would drive a distributor. Are you still running a coil rail with no way to bolt it down? I run the coil rail eliminator which used a coil pack and spark plug wires