So.. Obviously my previous post didn’t make any sense as blow back engine grease cannot get inside the rear Cat.CLEAN Your CAT - Fix stubborn P0420
Here's what I did: On 2005 Forester XT with P0420,
1. Removed downpipe/catalytic converters.
2. Separated into upper Cat and lower Cat.
3. In a 5-gallon bucket, mixed 4 gallons water, 10 oz. Citric acid and 7 oz Oxalic acid. (Purchased on Amazon - $20)
4. Soaked main Cat in acid overnght, rinsed completely with water.
5. Soaked upper Cat about 8 hours, then rinsed completely with water.
6. Reinstalled Cats, ran engine until hot, then cleared P0420 and it never came back. DONE.
P.S. For those of you that may be concerned about handling ACID, don't worry, just WEAR RUBBER GLOVES.
The oxalic acid is what's in "Bar Keepers Friend" cleaning powder that you buy at the grocery store, and
citric acid is commonly used in food to give it a "tangy" flavor.. Relax - it's not dangerous at all.
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I know you said the code hasn’t shown up again.. Would like to know if this is still the case after almost a month..
Does anybody know more or less how long are the precious metals inside the Cats which perform gas exchange supposed to last? Maybe all it’s needed is actually replacing the Cat itself, which might not be worth it if your car is older like mine or if you need to pass emissions.. just rather get the $5 fix instead.. not really what I’d like to do since it’s just cheating the O2 sensor, but if it’s not going to affect performance, I might just go this route.
Wondering though if anyone has gotten the code back after replacing the Catalytic..