Are you using the two different ECU's in your other thread? Also (I'm not sure if this actually works) have you tried pulling out the negative on your battery to see if the ECU resets?

 

Yes. I tried the original ecu and one from a '95. I had disconnected the battery each time I swapped them out. I might try to swap the proms from the '95 to my original. Not sure if this is the solution but it was suggested here and it might be worth trying.

 

I just reread this thread and saw that you said you had just replaced the cats. I've heard of the possibility that the cats might have been ruined because of the O2 sensor malfunctioning...
let's hope it's not that but it could be a possibility.

The guy told me that it's a possibility with me since high levels of NOx could point to ruined cats.

 

I wouldn't be totally surprised if the cats were done on mine also. The drive cycles have completed and are ok for everything except cats. It also smells weird - the exhaust fumes I mean. Not that I'm an expert on what the fumes should smell like, but I don't get this smell around any other cars. If I need to replace the cats I'll probably have to sell this car. It still needs some front end work which I was deferring until I got it to pass smog. 2 months later and still cant pass smog. It's not looking good.

 

How do you determine that the drive cycles are complete? And I was also getting a weird smell out of mine after I replaced the cats but before the O2 sensor replacement but now the smog guy said it's gone so hopefully that's a good sign for me.

That's unfortunate if it's your cats, maybe try getting them replaced through warranty from wherever you had them done or find used ones?

 

After about 2 months of trouble shooting and trial and errors trying to get my XJ6 to pass smog, it has finally happened. Took it in on Sunday and passed with flying colors, the guys said it was like the car was brand new.

The things I changed from when I purchased the car was
1. Spark plugs
2. Ignition coils
3. Rear catalytic converter and new exhaust from the cats and back, new pipes and removed the resonators
4. Replaced all fuel injectors
5. Changed out the front O2 sensors
6. Replaced the engine ECU but put back original as it wasn't the problem
7. Replaced rear O2 sensors with known working ones

I'm not sure if replacing the rear O2 sensors was the actual problem from the beginning or if it was a combination of all those things that actually fixed my problem but just wanted to list down all the things I replaced in case someone else ran into the same problems, they could get an idea of what to look at.

PS, after replacing the rear O2 sensors, I ran the car for about 90/100 miles but my NOx levels were still too high so I went to walmart and got a bottle of the Lucas Deep Clean Fuel system
and ran a full tank of that and got it tested again which helped it pass I guess.