chiken

That does sound like some bad cats. Given your gas mileage I don't think you are running too rich, I've brought my car up from 16.5 MPG to about 19 lately in a matter of about 5 weeks just getting the car back to they way it's supposed to run and from what I've seen on the gas mileage threads, 21-24mpg is on the high. One thing that you may find when these are pulled out is that the previous owner may have pulled the cats and gutted them (common practice on SC400's when you don't have to deal with emissions) especially since you said they are the factory ones all welded up. You usually don't have to break them apart and reweld them to gut them but who knows what the previous owner did. You may have been testing without cats the whole time. As for the center main cat, depending on if your car is a california emission car, that may be a cat and may just be a resonator, either way it's benificial to get rid of it and put a good quality high flow cat in it's place. There are plenty of threads as to which is the best cat to use, you might want to check this thread and see what cats people have had luck with in the past. https://www.clublexus.com/forums/per...st-thread.html I haven't paid too much attention to the cats because I plan on removing mine as well since I'm in Florida.

Supra Dr

iTrader: (14)

Would have really liked to see the #'s w/o the alcohol.
HC is high even w/ the alcohol & NOx is threw the roof.

Before you start messing w/ the cats, I would check the front or up stream O2's &
thoroughly check the EGR system. Cleaning the EGR may not be the problem.
The solenoid & vacuum modulator are both high failure parts. There should be
a thread on how to test everything here somewhere.

If the front O2's are bad, the rich condition may kill your new cat down the road &
you will be back in the same boat. I've never successfully 'cleaned' an O2 & had
it work properly. O2's are a wear item just like a spark plug. Cleaning i think is
a internet myth, may work 1 in a 100 times maybe. W/o a scan tool, lab scope
or analog meter there is no way to know.

Ali SC3

iTrader: (10)

does your first post say that overdrive is off? thats not going to help your emissions at all it should be on.
If you are that much over it is most likely your cats, it really cant be much else if its that bad or your car wouldn't be running right. 180k is alot for the stock cats. just get 2 universal magnaflows and have them welded where the current ones are. or use it as an excuse to upgrade the exhaust.

chiken

The main thing that makes me think that this is not a "rich condition" problem is the fact that his gas mileage is what it is. Especially if his numbers are that high you would think that his mileage would be a bit less. He could could a voltmeter and do a quick test on the O2 sensors to see if they are switching properly or if they are staying rich etc. The correct way to go about this would be to just go through all the general specs, check all sensors, injectors, cats for proper operation. If it were a bad injector you would see one bank stuck rich while the othe ris operating properly.

I would at least want to pull down the exhaust and take a peek at the cats to see the condition, it just seems very strange that someone would weld them up like that, they are pretty easy to unbolt and remove for the most part.

Supra Dr

iTrader: (14)

How I understood the exhaust welding was the flanges on the rear of the cats rotted off &
someone welded the resonator pipes directly to the cats. (now 1 piece)