USP 3.0, bad cat replacement?

[wildweezel]

My '04 USP 3.0 may have a bad left catalytic converter...the factory cats were discontinued in 2020. We have C.A.R.B. standard emissions here in Colorado though.
Nobody will ship a non CARB compliant (i.e. Federal emissions standards) cat to Colorado though...and it seems as if nobody on the planet makes an aftermarket CARB cat for the A4 3.0 six MT at all. What're my other options? I'm already running expired plates while trying to figure out what to do.
I've already put more money into the car than I paid for it & it's only got 179,000 miles on it. I'd really hate to get rid of it.

Sent from my SM-A326U using Audizine Forum mobile app

[nick1980]

Check engine light for p0420?
Wonder if you can use an o2 spacer
Maybe worse case you’ll have to remove the cat and hollow it out(piggie pipe)then use the o2 spacer on rear sensor

[EuroxS4]

Do not hollow out the cat as someone suggested this is possibly the worst thing you could do. Using a spacer on the rear o2 will not solve your problem as the rear o2 measures both temperature and o2 in the exhaust stream. Ideally in my opinion the somewhat gray area of fixing this would be to run the test for cats via VCDS and find out that the g/s in term of flow needs to be seem by the rear o2 to equal a pass result. Then modify the map for catalyst in the ecu and make the flow g/s that you are failing at a good value in the catalyst map that would equal a pass result. Like I said this is a gray area however doable. Only other choice would be to remove cat and try to clean it using chances are the cat has some blocked honeycombs inside soaking in a solution to dissolve the blockage would be ideal or do it the ecm way.

[road_tripper]

you might try shipping a non-CARB cat to a UPS store in a neighboring state, and pick it up at the store.

[EuroxS4]

Non-carb will most likely be of shit quality as they all are. Will probably throw the same code upon install. These cars are sensitive in that respect.

[road_tripper]

I installed an Eastern Cataliytic (non-CARB) 12 years ago... lasted 31,700 miles and 1.5 years before throwing codes.

[road_tripper]

OP, visit a few 'old-school' exhaust shops in your area... they may be able to weld in a carb-compliant cat that your car will like, for a price that won't kill you. I recently had a shop weld in a new flex pipe and they were able to do it without dropping the exhaust for $90.

My passenger side cat lasted 300,000+ miles before finally throwing codes, hopefully yours is as burly :)

My city allows one emission subsystem to be 'pending' so I can still pass smog although both cats are bit 'inefficient'

[codemode]

I have an O2 spacer on my 1.8T. It has a mini cat built into it and it works wonderfully. No codes at all.

[Turbo510]

I have an O2 spacer on my 1.8T. It has a mini cat built into it and it works wonderfully. No codes at all.

A mini cat? Sounds like a marketing gimmick, but tell us more.

[Kevin C]

Also google converter cleaning. There are a few people posting positive results with a method based on a research paper. It involves taking the converter out and a chemical bath. Might be BS but there are a number of people that have had good results.

[Gin+]

I've had good luck with sensor tricks (elbows, etc) in the past.

[Fahrvergnugen]

I’ve had excellent luck with Cataclean from OReallys…. Follow the directions for sure, use pure, high octane gas, and pretend you and the car are Italian….

[Kevin C]

Post I was referring to" https://ecomodder.com/forum/showthre...hod-35264.html

https://pubmed.ncbi.nlm.nih.gov/16570632/