Catalytic converters...just checking to make sure I've done it all

[charm]

I know, there are tons of posts on this, I've read most of them. I just want to be certain I need to take the plunge and buy new converters.

 

I've owned my 2000 OB, 2.5L auto for a little over a year. It currently has about 150k on it, about 25k more than when I bought it. I bought it with blown headgaskets, talked the seller down $3k, and took it to my mechanic for a complete reseal. I took it to Smart Service here in the Seattle area so I'm certain the job was done right.

 

The 00420 CEL code was on when I bought the car as well. Smart Service suggested replacing the cats, but, having just dropped $3k for a reseal, I didn't want to spend the cash on OEM cats. They suggested Bucky's in Lynnwood. They replaced the cats with high flow, I don't recall the brand, cats and a new front O2 sensor.

 

There was another CEL, this one my fault, resulting from accidently using a wiring harness as a place to tie something down. By the time I took care of that CEL, the 00420 was back. I mention this because I really have no idea when the 00420 code came back.

 

I just replaced, yesterday, the rear O2 sensor and the CEL is back on.

 

I suppose the next step is to try SeaFoam, but after that, is it new cats? I'm unemployed and the thought of replacing something that expensive a year after replacing is horrifying.

 

Is there a step I'm missing?

 

Is there a non-OEM brand that anybody would recomend that would save me a few hundred dollars?

 

Is there a good exhaust shop in the Seattle area? I'm afraid to take my car back to Bucky's...the reasons for that are another long story.

[idosubaru]

have you verified the front sensor(s) are good?

 

you mention some electrical wire you zip-tied somethign too which apparently caused problems. check there for recurring problems.

 

Subaru has a drive-test procedure for verifying cat verses sensor issues. Of course I'm doubtful you'll want to pay for that.

 

I just bought a catalytic converter for a friends legacy on Ebay for $114 ( part plus shipping).

 

I would think the replaced cats should last more than 25,000 miles even if they are aftermarket.

 

That being said I'd check the Subaruoutbackforum, they seem to have a lot of experience and information on this issue over there. There are even folks that replace the cats without fixing the problem.

 

can you do the work yourself. aside from rust this piece is actually really easy to replace. 4 bolts and you're done.

 

good luck.

[StructEngineer]

I've used magnaflow (car sound) replacement cats with no problems. Would stay away from Catco, random technologies, and eastern catalytic.

 

The P0420 means your secondary o2 output isnt flat enough due to the catalyst not doing its job. So if you already replaced both sensors, and have an essentially new cat, the only other option would be to check for exhaust leaks in the off chance that they're messing with catalyst efficency.

 

My bet is ol Bucky used a POS converter. Consider buying a direct bolt on converter if possible and do it yourself. They're not bad unless they've done some cutting/welding that would require more work.

Edited May 31, 2009 by StructEngineer

[OB99W]

I know, there are tons of posts on this, I've read most of them. I just want to be certain I need to take the plunge and buy new converters.

[...]

Is there a step I'm missing?[...]

Is the front O2 sensor OEM? If not, it might be the cause of the problem.

 

Pre-sensor exhaust air leaks can trigger the P0420 code.

 

Any problem that causes the engine to output hydrocarbons sufficiently excessive to overwhelm the cats can cause the code. Aftermarket cats might not be as efficient as OEM ones, making it more likely that an out-of-spec mixture could tax them.

 

If you have access to an OBD-II scan tool (not just a code reader), some real-time data could help pinpoint the problem. Fuel trim numbers, etc., might reveal something.

 

If you can't do a scan, let us know how the engine seems to be running in general. Specifically, what gas mileage are you getting?

 

See: http://www.motor.com/magazine/pdfs/102006_09.pdf

Also, not Subaru-specific, but informative:

http://www.wellsmfgcorp.com/pdf/counterp_v7_i3_2003.pdf

http://www.wellsmfgcorp.com/pdf/counterp_v7_i4_2003.pdf

[charm]

The wire I broke was to the vapor recovery canister. The only reason I mentioned it was that the CEL from that masked the time frame that the 0420 code came back. That has been fixed.

 

The runs fine with gas mileage, mix of city and hwy, ranging in the mid twenties (24ish). It's been pretty steady at that for about year not wavering more than 1 or 2 mpg and that usually from hard mountain driving during ski season.

 

I beleive Bucky's uses magnaflow cats, but I'll double check. They rebuilt the bolt in piece without touching anything outside of that. As a result, I 'should' be able to replace everything with a new bolt in replacement.

 

That said, with everything new (25k miles or less) in that system, it just seems like it's something else. Perhaps an exhaust leak is the answer?

 

Does anybody know of a good, reputable exhaust shop anywhere in the Seattle area? It seems like I could save a fortune by having a good shop search for an exhaust leak. If there is one, it sounds like a little bit of welding or a new gasket could be the answer.

[subaru360]

I have this problem with aftermarket cats often. They don't work as well as the factory ones and you get a 420 code. You can try the anti-fouler trick. Buy 2 spark plug anti-foulers that will thread onto the oxygen sensor. You'll have to drill one out so the sensor will fit into it. Thread both on the sensor and re-install. This pulls the sensor back out of the exhaust stream so it reads less oxygen and will usually solve the 420 code. It costs less than $10 to do, so it's worth a try.

[charm]

I've read this over and over again and never seen the follow up question. What I've read is that aftermarket cats don't work as well. What I want to know is why not?

 

I could some sort of argument made for the increase in air flow with a high flow cat, which I have, but otherwise, the matrix in the cat should heat up, burn off the nasty stuff, and exhaust it out the back with the rest of the gases, right?

 

So what is the difference between OEM and aftermarket?

[OB99W]

So what is the difference between OEM and aftermarket?

A primary difference can be the amount of catalyst. Since a major component of the catalyst uses precious metal (platinum/rhodium/palladium), it simply costs more to have more. Some aftermarket manufacturers cut corners.

 

The less catalyst there is, the faster the converter can become inactive (''poisoned'') by contaminants in the exhaust. Those can be from antifreeze getting into a combustion chamber, certain oil and gas additives, etc. Also, too much unburned fuel can cause destructive melting (however, your reported 24 MPG suggests that isn't likely happening with your car).

[idosubaru]

Aftermarkets use less catalyst in them than stock converters, and it makes sense as there is a useful market for them. The idea is that aftermarket converters have far fewer miles put on them then stock. Stock converters easily see 100k-200k where as the average for aftermarket converters would be substantially less.

 

This is also why, during good markets, stock converters are worth 5 times aftermarket converters for scrap. That catalyst is most of the value.

 

Based on that valuation you can assume that stock converters have *roughly* 5 times as much catalyst in them.

 

If you then assume quantity of catalyst is directly proportional to usage then you could roughly say a stock converter makes 125,000 and an aftermarket makes 1/5 of that or 25,000 miles.

 

Sorry

[charm]

Using the valuation argument for why an OEM product is better than an aftermarket doesn't work.

 

That would mean that there's twice as much acid in a battery. Twice as much filter in an oil filter. You name, it's twice as much if it's stamped Subaru (or Honda, or Toyota, etc).

 

As far there being 5 times the catalyst, well, not sure that makes sense to me either. More than any other, the catalytic converter is heavily regulated and they just couldn't sell the things if they didn't do at least a mediocre job. Twice the catalyst I could probably get behind.

 

The next question is, who builds the catalytic converters that Subaru stamps as their own? Without the Subaru stamp, they're hald the cost.

[idosubaru]

sorry for the extrapolation, i by no means meant that as fact, just a fermi-problem.

 

it doesn't matter - the fact remains that aftermarkets have less catalyst in them, hence their lower value. lower costs and lower scrap yard prices.

[idosubaru]

sorry for the extrapolation, i by no means meant that as fact, it was to solidify a point - not necessarily be accurate.

 

aftermarkets have less catalyst in them, hence their lower value. lower costs and lower scrap yard prices.

[OB99W]

Using the valuation argument for why an OEM product is better than an aftermarket doesn't work.

 

That would mean that there's twice as much acid in a battery. Twice as much filter in an oil filter. You name, it's twice as much if it's stamped Subaru (or Honda, or Toyota, etc).

There's another dynamic working when it comes to catalytic converters that you might not be considering. The car manufacturer has to contend with the EPA-mandated emissions warranty for new vehicles. It would make sense for Subaru/Honda/Toyota/etc to use a part that isn't likely to fail during that period. Assuming the OEM replacement is equal to the original, it also should be expected to have a long life.

 

Aftermarket converters only have to have catalyst that makes it 25,000 miles to satisfy the EPA. See: http://www.catalyticconverter.org/news/news_page.cfm?Key=catalytic_converter-&News=20

 

Still not convinced of the difference between OEM and aftermarket? Then see this, which starts off explaining that ''high flow'' is misleading, and then what the differences are in cells/inch and amount of catalyst used: http://www.catalyticconverter.org/news/news_page.cfm?Key=catalytic_converter-&News=89

[StructEngineer]

Yup, stock converters must last longer, therefore more catalyst.

 

I just changed one out last weekend. The stock cat's bricks were twice as thick as the aftermarket.

[charm]

Stop telling me what I don't want to hear. The guy at the muffler shop told me the same stuff after he told me there was no exhaust leak. He did suggest having my mechanic running some more indepth diagnostics to be absolutely certain it is the cats. But he's pretty sure it's the cats.

 

I can also hope that I have an O2 sensor that failed before its time...that would be cheaper. I could also hope that the rear O2 sensor, the brand new one, is faulty.

 

One can hope!

[johnceggleston]

Stop telling me what I don't want to hear. The guy at the muffler shop told me the same stuff after he told me there was no exhaust leak. He did suggest having my mechanic running some more indepth diagnostics to be absolutely certain it is the cats. But he's pretty sure it's the cats.

 

I can also hope that I have an O2 sensor that failed before its time...that would be cheaper. I could also hope that the rear O2 sensor, the brand new one, is faulty.

 

One can hope!

 

if the rear o2 sensor was oem, here's what i would do (assuming the o2s for 00-04 are the same as 96-99):

 

remove the rear o2 sensor and splice it onto the connector for the front o2 sensor, and install it. now your high dollar subaru o2 is where it needs to be. buy a generic o2 for the rear sensor (maybe move the front one to the rear). reset the codes and see what happens.

 

in the 96-99 legacy/outbacks, the p0420 means your front sensor is bad and it has to be a subaru part. your year may be different.

Edited June 1, 2009 by johnceggleston

[OB99W]

Stop telling me what I don't want to hear. [...]

If you reread my post #4 in this thread, you'll see that I suggested some possibilities for P0420 other than actual catalyst inefficiency. (And yes, the front O2 sensor should be Subaru OEM -- it can make a difference.) A competent mechanic should be able to do a diagnosis that will either confirm alternatives or rule them out.

 

Here's more info, including some causes of P0420 to consider: http://www.catalyticconverter.org/news/news_page.cfm?Key=codes-po420-po421-po430-po431&News=120

 

By the way, I have no particular predjudice for OEM parts, other than when experience shows it makes a difference in certain applications. Sometimes the advantage is performance or longevity, and sometimes it's just that a part fits without having to ''modify'' or ''persuade'' it.

[charm]

It sounds like there are several things that can also be checked...just not by me. I made an appointment with my mechanic for Thursday for a full diagnostic.

 

Both O2 sensors are OEM. The front has about 25,000 miles on it and the rear about 250 miles. Give or take anyway.

 

The cats were replaced with the front sensor.

 

Even the guy at the exhaust shop mentioned how picky Subarus (and BMW's) were with cats. He did mention that he has found the new bosal (sp?) cats for the Subarus are working well. He stopped installing them on Subarus for a long while because of a 30% failure rate. His theory was that the metal content in the old ones was too low. The new ones appear to be better. He also suggested playing is safe for not a lot more money and ordering the part from Subaru.

 

So, the muffler shop won't even tell me what I want to hear. All I wanted to hear was that there's an exhaust leak, but noooo, that was too easy.

[StructEngineer]

I like to play it safe when it comes to parts, but when the OEM part is 4x more expensive it doesn't make sense to buy it.

 

BTW, are you in a state that monitors emissions? A 2 cent piece of electrical tape on your dash light does wonders.

[OB99W]

The link I gave in post #17 of this thread for causes of P0420 no longer works. Here's a new one to the same info:

http://www.catalyticconverter.org/news/news_page.cfm?Key=catalytic_converter-&News=120

[bgambino]

I have this problem with aftermarket cats often. They don't work as well as the factory ones and you get a 420 code. You can try the anti-fouler trick. Buy 2 spark plug anti-foulers that will thread onto the oxygen sensor. You'll have to drill one out so the sensor will fit into it. Thread both on the sensor and re-install. This pulls the sensor back out of the exhaust stream so it reads less oxygen and will usually solve the 420 code. It costs less than $10 to do, so it's worth a try.

 

Anyone....will doing this have any adverse effect on performance or gas mileage?

I thought that this may send wrong signals to the ecm..?

[kami333]

Nope, rear one is just for monitoring the cat(s). Messing with the front one will affect fuel/air ratio, etc.

[charm]

OB99W, is that link (http://www.catalyticconverter.org/news/news_page.cfm?Key=catalytic_converter-&News=120) saying that bad spark plug wires can through a P0420 code?

 

With all that I've read on here about using only Subaru or Magnecor wires I've been a little paranoid about the fact that my mechanic installed OEM NGK wires. I just don't see how they would cause a P0420 code and not any other code.

[OB99W]

[...]I've been a little paranoid about the fact that my mechanic installed OEM NGK wires. I just don't see how they would cause a P0420 code and not any other code.

Defective/inadequate ignition wires can cause misfire, and sufficient misfire can cause P0420 to be triggered. A small amount of misfire won't cause a misfire code (P030x) to be triggered, and a cat that's working correctly should be able to handle a little misfire without triggering P0420. If you're not getting any misfire codes (may be pending), and can't detect any roughness in engine running, then the ignition wires are probably not the cause.

 

A decent scan tool (not just a code reader) can give some insight into the problem -- freeze frame and other data could provide good clues as to what's happening. An exhaust gas analyzer would also be a useful tool. Even just knowing what both O2 sensor outputs look like would help immensely. Without that kind of info, it's likely to remain hard to pin this down.

[charm]

The mechanic ran everything today. Everything checked out pretty normal. The guess was the front O2 sensor...and it is just a guess. The reason for the guess is that the plug on the O2 sensor was damaged when the last new catalytic converters were installed.

 

The shop that I will never again let touch my car, Buckey's in Shoreline, WA, forgot to plug the O2 sensor in after installing the cats. Instead, the wire harness was draped over the axle and the plug was resting on the brand new cat. The plug melted a bit. Bucky's just scraped out the melted plastic and plugged it in. I was too sick of their crap to argue.

 

The theory is that because the plug is damaged it's intemittently losing some connectivity. Again, it's a theory. The codes were reset and we'll see if the CEL comes back on.

 

The car runs smooth as silk and there are no codes other than the P0420 so I seriously doubt the misfire. Whatever it is, it's hiding really well.