[Josh Sparrow]

So my 2002 outback H6 cats are definitely done. 275k OEM cats with many miles ran while the engine was running rough + oil contamination during a head gasket job. New O2 sensors installed too, cataclean ran through which cleared the P0420 code for maybe a week but it’s back.

So question is does anybody out there have any recommendations for what is a good direct fit aftermarket. OEM is ridiculously expensive, RockAuto has (daily driver) Walker, Bosal, (premium?) Eastern Catalytic and Davico. Any experience, Suggestions etc....

Thanks everyone in advance.


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[Numbchux]

I work at a Subaru dealership. We see failed cats somewhat regularly (mostly for '05-09 Leg/OBK, I'm not sure if there's actually an issue there, or if it's just a numbers/age thing, we work on a lot of them, and they're likely to get repaired). We spent some time trying aftermarket ones to try to save our customers some money.....

We saw a very nearly 100% failure on aftermarket ones within about a week. The Walker ones approved for California Sale seemed to last a few weeks before throwing a P0420 again. And Dorman seemed to be well into the second month.

I have the OBX Stainless header set from ebay and sensor spacers on our 2004, and I'm pretty happy with it. The code does come back occasionally with the spacers, but not very often. http://www.subaruoutback.org/forums...-04-outback-vdc-resurrection.html#post4093530

 

[idosubaru]

i'd install a spacer a well.

do you get excellent gas mileage and no oil use at all between oil changes?

another issue is often one can't verify that all possible contributing issues that may downgrade another converter are all addressed and the car is running perfectly....either a very expensive OEM one or lesser grade, less forgiving aftermarket.

ideally you see some accurate fuel trims, EGT's, exhaust temps, O2 signal analysis or whatever verifies that your engine isn't going to contaminate the next converter.

 

[Glennda5id]

The Walker California Emission Cat's are going to have a longer warranty and more precious metals. They do not sell direct fit ones but you can grab weld in replacements. Part number for the front left and right are 81806. The rear unit is 81613. Rockauto sells these parts but does not list them when looking up by vehicle. You need to search directly by part number. They come with a 5 year 50,000 mile warranty.

It should be pretty easy for a shop to weld in the fronts. Maybe a little bit more work to do the rear unit. If you go this route I would just start with the fronts.

Another option if you want to try to bypass the P0420 code is to install a diode inline with the rear 02 sensor. I haven't done this but it should work fine.

I recently was getting a P0420 pretty regularly. Then I started having some engine starting and driving issues and got a code for a faulty CAM position sensor. After the I replaced the cam position sensor my P0420 never came back. I am not suggesting you replace you cam sensor, but I think in my case the cam sensor was acting up and maybe causing some fueling issues which started tripping the P0420 code. I can't say for sure. I have the exhaust off now and ran a camera down inside and the cats are in fine shape. No visual damage or breakdown.

 

[Mad Mallard]

i've seen the aftermarket pipes available since I've replaced mine, I went with Eastern Catalytic from Rock

BUT!

if i had time to do it again, I would keep the stock pipe, take it to a metal shop, and have them cut out the old one and replace the material and weld it back up nice.

The construction of the stock pipes are just so much better, especially the bell housing at the block.

so if you have also gone thru the 0420 thread for causes and worked on them, and you aren't under a time crunch like I was, I'd keep the oem stuffs.

 

[Josh Sparrow]

So basically from what everyone is saying, don’t get the aftermarkets? That sucks, OEM was in the 2k+ area for all 3 cats....

Spacer? Not familiar with that. Could you elaborate any?

Gas mileage is around 20mpg give or take some. Fuel trims are a little off but I think it’s because of the cats.


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[Glennda5id]

I would not buy OEM cats for a car with 275k miles. I would replace the front two with the Walker CA CARB cats. They are $90 each plus cost to weld them in.

 

[Numbchux]

So basically from what everyone is saying, don’t get the aftermarkets? That sucks, OEM was in the 2k+ area for all 3 cats....

Spacer? Not familiar with that. Could you elaborate any?

Gas mileage is around 20mpg give or take some. Fuel trims are a little off but I think it’s because of the cats.


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Cats will not effect fuel trims unless something is clogged. Only thing new cats will fix is a P0420 code. I only replaced mine because they physically broke in 2 places

Oxygen sensor spacer, lots of ways to do it and parts sources, best to just search it here and elsewhere, very universal (virtually all oxygen sensors are m18x1.5 thread). I pictured it installed in my thread which I linked above.

 

[idosubaru]

Spacer? Not familiar with that. Could you elaborate any?

There's a variety of lengths and angles and you can get them for $5 but here's an example:
https://www.amazon.com/O2-Sensor-Spacer-Adapter-Extender/dp/B00CZFCPQU

remove rear O2, install that spacer, then install rear O2 back on top of it.

Gas mileage is around 20mpg give or take some. Fuel trims are a little off but I think it’s because of the cats.

Cats are unlikely to be causing wonky fuel trims on that platform. Unless they're clogged like he said but then we'd expect other issues.

Maybe the poor fuel trims are causing the converter issues?

Can you verify/test your O2 sensors?

20 mpg is on the low side but if it's city, short trips, or heavy on the foot at all that vehicle drops quick.

 

[Josh Sparrow]

Cats are unlikely to be causing wonky fuel trims on that platform. Unless they're clogged like he said but then we'd expect other issues.

I don’t think they’re clogged but won’t way it’s impossible. I have the rotten egg smell coming from the exhaust. As I stated before had run CataClean before that helped for a bit but not long.

Maybe the poor fuel trims are causing the converter issues?

Can you verify/test your O2 sensors?

I have freessm and RomRaider, Other than that all I have is an old analog voltmeter.

20 mpg is on the low side but if it's city, short trips, or heavy on the foot at all that vehicle drops quick.

20mpg is about average, most of it is a mix of city and highway. On long interstate drives I get a little over 22mpg and I do tend to be a little heavy on the petal as Kentucky drivers tend to require you to be more aggressive behind the wheel.



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[Josh Sparrow]

Alright, after some thought, I guess I’ll have to put the cats on hold for now. Installing the rear strut assemblies this weekend.

Then I’ll focus on troubleshooting my evap P0447 CEL code and try to figure out what’s wrong with the fuel trims and maybe run another thing of cataclean.

Then once I know nothing mechanically or electrically is wrong I’ll tackle the cats somehow.


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