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2002 Outback, 2.5L SOHC w/ 170k mile
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Discussion Starter #1
I've replaced my cat because the stealership said it needed one (I took it to a muffler shop), replaced both o2 sensors when a year and a half later it threw the P0420 code again, that solved it for a little while and now it's back again.

So... I heard, and it seems sort of crazy, to throw a gallon of lacquer thinner into the half-full gas tank and it'll clean it out and I can clear the code. Seems a bit extreme and rough on my baby's engine.

There's also liquid catalytic converter cleaner (cataclean) I can put in the gas tank. Not sure if it'll work or if it's too far off from the lacquer thinner theory.

A friend's mechanic friend has been using high proof alcohol, like a 190 proof, in tanks for years and says it works. Again, I'd rather not burn out my engine if it's going to blow up the car.

Then I also read about just dropping the cat and using something like Tide for your clothes in water and soaking it overnight.

For the discussion and replies: What have you used and did it work? The **** CEL is robbing my MPGs. I also read it turns on as soon as you hit 94% efficiency?

I have no problem jacking the car up and using a cleaner on her, just want to know it'll actually work when I do that.
 

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03 H6 OBW & 06 WRX Sportwagon
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I'd be particularly hesitant to run anything not sold over the counter for use in a gas tank. Even then, I'd stay with a known name-brand like SeaFoam, Techron, etc.

i have read that there is a method for 'cleaning' a cat. conv. dropped from the system using a citric acid bath. O doubt it works on every problem a conv. could have, but it may work.

But, you should first know, that it's uncommon for a cat replacement to solve a P0420 CEL code issue. There are MANY problems that lead to that code. A bad cat conv. is only one - and not the primary one from what I've read.

read here; http://www.subaruoutback.org/forums/66-problems-maintenance/49537-p0420-diag.html?highlight=p0420
 

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Not to mention a bad CAT is down stream of what generally causes the actual failure of the CAT its self. Sensors giving a CAT error are simply indicating that the emissions readings are wonky and there are lots of things that can cause this but the least common is the very simple zero moving parts or electronics CAT.
 

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2002 Outback, 2.5L SOHC w/ 170k mile
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Discussion Starter #4
Well, I cleaned the OEM o2 sensors, bought Bosch sensors and used those, new PCV valve, new MAP sensor, battery is new and good, new spark plugs and racing quality spark plug wires in the last two years. Quite a bit of work in order to do anything but mess with the cat itself. Also, maybe or maybe not related, replaced heads, water pump, thermostat, timing ect. Run Mobil1 through her.

When I did the big head job I also replaced the gasket just before the cat as it was leaking after we messed with the headers. The PCV valve was done and there are no intake or exhaust leaks. Also, the intake manifold has new gaskets. Did a whole lot of reseals on the entire intake/ exhaust system.

We didn't start with the cat, we eliminated everything but it.
 

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Well, I cleaned the OEM o2 sensors, bought Bosch sensors and used those, new PCV valve, new MAP sensor, battery is new and good, new spark plugs and racing quality spark plug wires in the last two years. Quite a bit of work in order to do anything but mess with the cat itself. Also, maybe or maybe not related, replaced heads, water pump, thermostat, timing ect. Run Mobil1 through her.

When I did the big head job I also replaced the gasket just before the cat as it was leaking after we messed with the headers. The PCV valve was done and there are no intake or exhaust leaks. Also, the intake manifold has new gaskets. Did a whole lot of reseals on the entire intake/ exhaust system.

We didn't start with the cat, we eliminated everything but it.
It's well known for a long time now that the front O2 needs to be OEM the rear can be any brand. This is related to the very specific OEM feedback to the ECM. So if you went non OEM on the front O2 that is probably your issue as many people have learned this the hard way for a long time now.
 

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03 H6 OBW & 06 WRX Sportwagon
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I believe cardoc once explained there is a propane test for cat. convs. i have no idea how one would find a shop doing that.
 

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03 H6 OBW & 06 WRX Sportwagon
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It's well known for a long time now that the front O2 needs to be OEM the rear can be any brand. This is related to the very specific OEM feedback to the ECM. So if you went non OEM on the front O2 that is probably your issue as many people have learned this the hard way for a long time now.

^^^yep

we'd also like to know what plugs you installed.
 

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^^^yep

we'd also like to know what plugs you installed.
LOL - yep oddly enough subaru is famously picky about the spark plugs NGK with really good quality wires more or less avoids any type of problems. Any other brand plugs there is always a stream of forum threads of people asking why their car runs like garbage after changing their plugs.
 

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2002 Outback, 2.5L SOHC w/ 170k mile
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Discussion Starter #9
NGK on platinum plugs and NGK wires, Bosch is OEM for the O2 sensors so I bought those
 

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2002 Outback, 2.5L SOHC w/ 170k mile
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Discussion Starter #10
Also bought my replacement MAP at the dealership since the shop wanted like 250 to do it for me. Picked one up that day and swapped it out in the PepBoys parking lot
 

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03 H6 OBW & 06 WRX Sportwagon
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I thought Denso was OEM A/F sensor?

Do you have access to a code reader that can retrieve freezeframe data? might be interesting to see if the fuel trims are way off.

maybe someone can suggest a good mechanic in your city to help troubleshoot the problem.
 

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Car: 2008 Tribeca, 2010 LGT, Sold: 2005 XT Limited
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You are going to have to get some software to log your sensor parameters to figure out what is really causing the code. No other way to troubleshoot it in the end. Everything else is just guessing. You will also need some help interpreting the results (Cardoc has been very helpful with this in the past).
 

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I thought Denso was OEM A/F sensor?

Do you have access to a code reader that can retrieve freezeframe data? might be interesting to see if the fuel trims are way off.

maybe someone can suggest a good mechanic in your city to help troubleshoot the problem.
Denso is - but not sure if that is O2 also. However Bosch bought at the parts store and Bosch bought from a dealer doesn't mean the specs are the same regarding electrical feed from a sensor.
 

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2002 Outback, 2.5L SOHC w/ 170k mile
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Discussion Starter #14
My reader is basic and just tells me codes. I can ask some mechanical friends to see if anyone has access to a more intensive diagnostics system. I'm also going to try the citric acid as I read that's better than a soap bath (has do do with oils getting on the cat, correct?)

I generally am avoiding shops right now as I got ripped off at stealerships, the local subie dealer insists the new 2012 Impreza I have burning through a few quarts of oil is 'within acceptable parameters' and the idiot that worked on my F150 shoved kleenex into the dash to cover up a flashing airbag light. (He's got the BAR and BBB on his ass right now).

Plus Cali is run by idiots and CARB makes me angry. Rather not have a muffler shop with a million and a half regulations on their backs work on it.
 

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A cat is basically basket full of precious metals that heat up and react with the exhaust gasses. Anything you put through it that eats the precious metals is doing just that eating the cat.

You need to get the system read to figure out why its giving you the error. The CAT is just the down stream part that you are targeting as the cause when its probably not the cause and sending metal eating chemicals or acids through your CAT is just silly if you understood how they worked and what those chemicals are doing to it.

Your issue is your sensors and ECU picking up errors and you need to find out why its giving you those errors the CAT is just getting the short end of the stick.
 

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Car: 2008 Tribeca, 2010 LGT, Sold: 2005 XT Limited
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I believe an OBDII cable to usb and the software that comes with those will be able to monitor the sensors live, but I haven't looked in to it for a Gen2 car.
 

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Also interested in experimenting with cat-cleaning...

I was literally about to go for it on a 2000 2.5 (throwing a MIL, no CEL) and decided to scope posts for any info. Viola!

My idea was to take MAF spray-cleaner and bolster the can's propellant using compressed air to howl it through the removed Cat.

I like the soaking idea better.

Okay, so certain chemicals will eat the Cat's platinum (etc.), but it seems reasonable to believe that some will not.

After eliminating all of the very good real-world reasons that a 420 code (v MIL CAT "Not Ready" ?) could be a pre-Cat problem, why not at least TRY a cleaning solution prior to forking out the bux for a new Cat?

Gleaned from other posts, it sounds like there are multiple ways a Cat can fail. Coating/caking the precious metal surfaces with crap (carbons?) can prevent the pollutant 'absorbing' characteristics of the Cat's function, and the other primary failure sounds like 'cooking/melting' the precious metals through pre-ignition ( a litany of possible causes from poor fuel, old tune, valve issues, etc).

Since there's essentially no damage liability to a condemned Cat already on death-row (pardon to non-US/Saudi/China residents), what's the harm in attempting to eliminate the variable of a 'dirty' cat by using a non-destructive cleaning method?

Immersion in a fluid-circulating parts-washer would seem the best method, probably less the insanely caustic parts-washing solution. I'd go that route except the pump died in mine, other priorities.

Consensus on cleaning products and methods?

Maybe Seafoam mixed in a bath of... cheap vodka?
 

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2007 OBXT Limited, 5MT 148K
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If you've got access to an IR thermometer ($30 at Harbor Freight) you can run a very simple test to determine if the cat is functioning. Run the engine at 2,000-2,500 rpm for a couple of minutes. Using the IR thermometer, check the pipe temperature at the inlet and outlet of the cat. A properly functioning cat will have an outlet temperature that's higher than the inlet temp. If both readings are the same, or the outlet is slightly cooler, the cat isn't working.

A properly working cat is self-cleaning; i.e. you don't need to do anything to it.
 

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03 H6 OBW & 06 WRX Sportwagon
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I was literally about to go for it on a 2000 2.5 (throwing a MIL, no CEL) and decided to scope posts for any info. Viola!

My idea was to take MAF spray-cleaner and bolster the can's propellant using compressed air to howl it through the removed Cat.

I like the soaking idea better.

Okay, so certain chemicals will eat the Cat's platinum (etc.), but it seems reasonable to believe that some will not.

After eliminating all of the very good real-world reasons that a 420 code (v MIL CAT "Not Ready" ?) could be a pre-Cat problem, why not at least TRY a cleaning solution prior to forking out the bux for a new Cat?

Gleaned from other posts, it sounds like there are multiple ways a Cat can fail. Coating/caking the precious metal surfaces with crap (carbons?) can prevent the pollutant 'absorbing' characteristics of the Cat's function, and the other primary failure sounds like 'cooking/melting' the precious metals through pre-ignition ( a litany of possible causes from poor fuel, old tune, valve issues, etc).

Since there's essentially no damage liability to a condemned Cat already on death-row (pardon to non-US/Saudi/China residents), what's the harm in attempting to eliminate the variable of a 'dirty' cat by using a non-destructive cleaning method?

Immersion in a fluid-circulating parts-washer would seem the best method, probably less the insanely caustic parts-washing solution. I'd go that route except the pump died in mine, other priorities.

Consensus on cleaning products and methods?

Maybe Seafoam mixed in a bath of... cheap vodka?
the last time read about it, citric acid was the choice for soaking the cat. You'll have to research the concentraion, time. methods.

citric is 'relatively' safe. I've used for removing scale/flux on jewelry after soldering so, likely safe for platinum and other PMs. But of course, your experience may vary. I think I bought a pound or 2 from some site selling candle-making supplies but, it's been a long time ago.

have you checked youtube?
 

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YOU CANNOT CLEAN A CAT...
You either ruin it(most of these cleaners will strip the precious metals), clog it(usually by overheating/melting the brick), or damage other components(by using lacquer thinner aka "panther piss).

My '01 was throwing the infamous 0420 code so I just ADDED a generic cat downstream and hooked the O2 sensor to that one. Cost me about $150 or so. The O2 wire is plenty long also...no more codes.
 
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