Restoring old catalytic converter's efficiency (cleaning method)

[Xist]

Nice! I will try this the next time I acid wash my cat!

[freebeard]

Interesting. My Dasher's injectors will be laying on a bench soon, if not already. So what's the best container material? Copper or bronze? And what's the proportion of water to HCL?

[California98Civic]

Originally Posted by freebeard

Interesting. My Dasher's injectors will be laying on a bench soon, if not already. So what's the best container material? Copper or bronze? And what's the proportion of water to HCL?

I just have a very simple, cheap Walmart pot. Steel? The acid is very mild, a mix of citric and oxalic in the proportion to water described in post #1 of this thread. Took my daughter to an appointment tonight and so far, still 100%. I hope to not see the P0420 code again. And if I do,I will be more confident that it is the CAT and not a sensor. Given that the head gasket was failing, it is not surprising that I have some exhaust system troubles. The CAT prolly needs help, too.

[Xist]

California98Civic, did the interior of your pot discolor? Mine is all grey now, then it rusted. I think the acid ate the stainless coating. The $110 cat turned green, too, but there could be other factors there.

[California98Civic]

Originally Posted by Xist

California98Civic, did the interior of your pot discolor? Mine is all grey now, then it rusted. I think the acid ate the stainless coating. The $110 cat turned green, too, but there could be other factors there.

Both the iron or steel casing around the catalyst and the pot discolored but neither in quite the way to describe. My pot is not rusting. I think I could probably scrub off the discoloration, but why bother when it is just for such industrial purposes. I rinsed it and left it alone.

[California98Civic]

P0420 code (catalyst efficiency) is intermittent but persistent. I can clear it and shut off the CEL but if it takes a day or a couple weeks it always comes back.

By August 2, I have to have a successful SMOG test. So this is the perfect chance to test the efficacy of the cleaning method in the OP.

Suggestions? (take a look at the OP).

Also, I think I will try swapping the upstream and downstream O2 sensors in one last test to see if I have an intermittent sensor failure. Bad idea?

[California98Civic]

Originally Posted by California98Civic

...

The formula & procedure:
Caution: do this outside in a well ventilated area and wear gloves and goggles. The acid is not particularly caustic, but you don’t want to get it on stuff unnecessarily. Also, while heating it produces a smell that would not be pleasant inside—and that might indicate something unhealthy.

Formula: Per gallon of water I used 75ml citric acid and 50ml Oxalic acid.

Procedure: I placed the CAT in my cheapo 12 quart pot. Two and a half gallons water nearly reached the brim and completely covered the catalytic converter inside the housing. So I mixed 225ml Citric Acid and 125ml Oxalic Acid with the 2.5 gallons water. Ideal temps for the solution are said to be 150-160* F for six hours. ...

I am all set up to do this wash in the morning, when I will have six straight hours. Since my car has set the P0420 code and I have to do a Cali SMOG test this month, we might get a pretty good test of how effective this procedure is.

Quoting myself for the procedure and formula details.

[California98Civic]

Cleaning went well. Took it for a drive with my daughter to get some drinks and snacks five or eight mikes up the freeway. Hung out. Drove back. No codes (yet). Does that count as one drive cycle or two? I think two.

The Ultragauge is so slow in sampling that I cannot really tell if the downstream sensor is getting better data. It was generally reading at a higher voltage (less oxygen). At first it stayed pegged at max voltage, long after closed loop. Then after a few miles it started to move a little, generally staying at 0.8 volts or higher. The other sensor moved all over the place as expected.

I will edit with some more pictures in a moment... gotta switch devices.

The set up. Neighbor's candle making thermometer was perfect.


Oily surface and black globuals floating in water one it heated up to at least 130*F


picture of initial closed loop screen after three miles driving... engine off in pic.

[Xist]

I like the part where every picture is pointed in a different direction!

[me and my metro]

As long as both sensors don’t swing together you won’t get the code. That is much cheaper than a new manifold.