Cleaning CAT to solve CEL

[Toolaa]

While I'm waiting for some parts to come in today to complete my lower end rebuild I found this thread on BITOG. Where this guy used citric acid and Oxalic acid to clean his CAT to remove the P0420 code.

http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3391904

I was planning on ordering an aftermarket CAT but I figure I may try this on the old cat to see what happens. I figure I've got nothing to lose while the car is on jack stands.

Does anyone know if the chemistry behind this approach could work?


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[chaos2984]

Well sounds to complicated and that how much more time will that buy you before the light comes back. I would just gut the cat completely and just use a spark plug non fowler and pull your rear o2 sensor out of the exhaust stream so it monitors less and you should make the light go out. Or just get a flash from apr. to have it not look at the cat. Thats what i did for my B5 s4 when i gutted the cats.

[Toolaa]

So I ended up trying this and so far it works. I've had the P0420 code for 6 months. Each time i cleared it it would come back within just a few miles. I tried adding one then two spacers to the post cat O2 sensor. It didnt work.

Well I put 100mi in the past two days after cleaning the CAT and no CEL or codes.

I'm going to put another 70mi tomorrow. I'll post the details of the mixture and time when I get back.


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[Toolaa]

Another 72mi and no codes.

Here is what I did. First make sure you have heavy rubber gloves and safety goggles (not just glasses). It's acid so it's dangerous. Make sure you don't have kids or pets nearby either.

Mixed 1/2 lb of Citric acid and 1lb of Oxalic acid (wood bleech) with 4gal of water in a 5gal bucket.
http://img.tapatalk.com/d/14/07/27/y8ugy3u8.jpg
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Then but the plastic bucket into a big pot we use to steam crabs. I had the bucket sitting on some metal rack to keep it about 2" from the bottom of the pot. Then I filled the pot with hot water and set the whole thing on top of my gas grill. Then submerged the cat.
http://img.tapatalk.com/d/14/07/27/tynapasy.jpg

Got the acid mixture up to about 150-160deg and started a timer for 8hrs.
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About every hour I would go check the temp and adjust up or down if needed. I would also use a hook to lift the cat from the water and then re-submerge it to redistribute the acid mixture through the cat.

After 8 hrs I turned off the heat and just let everything cool off for about 2hrs. When I pulled the cat out if the water it was very dirty.
http://img.tapatalk.com/d/14/07/27/egypuzyr.jpg

I rinsed it with tap water and then used my leaf blower to blast our all of the water.

That's it.

If there are no codes after a month i'll report back.


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[GeriatricGinger]

How hard is it to remove the cat? I was looking at it this morning, and it looks a tad on the tight side, unless I had two wrists on the same arm ;)

[Toolaa]

I had the engine out so it was easy. But you can disconnect the down pipe and pull both the cat and downpipe out through the engine bay.