question about catalytic convereters

[charm]

I've been wrestling with a P0420 code on my 2000 OBW with 170k mi on it for over a year now. I'm 2 sets of cats, 2 front O2 sensors and 1 rear O2 sensor into this. Both sets of cats have been aftermarket...I should have bought them from Subaru. And I do have the anti-foulers installed so at least my CEL is off, usually. But, my question is about the cats themselves. Presumably I'm I'm not burning off enough 'stuff' coming out of the engine. If I could make the cats hotter, would I, in theory, burn off more crud? My thought is this, if I take high temp exhaust insulating wrap and wrap it around the cats and the pipe between them, won't I burn off more crud thus improving the effeciency of my catalyst? Knowing the engine has been apart in the 40k miles to do the headgaskets and every other engine seal, the engine was clean. Where is all of this crud coming from that's throwing the code? PCV? Other sensor making me run too rich but not so out of whack as to throw a code?

[GeneralDisorder]

It's a balancing act - hotter will improve their effeciency AND decrease their life. I've seen just a few miles with a bad ignition component cause a cat to glow red and then throw catalyst effeciency codes immediately after the ignition was repaired. My neighbor's truck was running fine - he went to pass someone on the freeway, lost all power (engine started missing) and coasted to the side of the road. He waited for a bit - about 30 minutes later it fired up and drove home without problem. Replaced the ignition coil and then within a week both cats turn up bad according to the ECU. I installed non-foulers and it's fine now.

 

Just leave the non-foulers in place. Let someone else pay the premium for replacement parts. If the non-foulers aren't doing it then spend the $25 on a rear O2 simulator or add a 2nd non-fouler

 

GD

Edited April 28, 2010 by GeneralDisorder

[vic/se]

have you tried a hotter plug?

[charm]

have you tried a hotter plug?

 

hmmm? A cheap easy experiment. I like it! Burn more stuff, leave less for the cats.

 

What's the down side to a hotter plug?

 

I know the anti-foulers make the car think that everything is working properly, but it's not. I would prefer to fix the problem as opposed to working around it.

[idosubaru]

spark plugs would be an easy attempt (on non-DOHC anyway ). i would suspect Subaru converters are the fix, though i don't recommend it. wonder if two aftermarkets would be as good as Subaru OEM? good luck, this issue is one of the more annoying ones.

 

I know the anti-foulers make the car think that everything is working properly, but it's not. I would prefer to fix the problem as opposed to working around it.

technically you're working around yourself, but there's nothing wrong with that either. definitely good to feel good and confident about a car.

 

i say the following to ease any concerns you might have:

 

is using spark plugs still a work around? to me hotter plugs is the same thing. even installing new Subaru converters for no actual reason other than the catalyst efficiency CEL is a work around for the tight margins which are the problem here. it's just doing it with different parts.

 

your system is operating properly it's the tolerances being so tight causing the issue. in this case those tight margins gain zero value, so financially, mechanically, reliably, emissions, and functionally there's nothing to gain. an ECU can be built that has even tighter restrictions and margins and would require more money, work and time to maintain.

 

a computer could monitor everything on your car and see deficiencies in something...fuel performance, gas mileage, spring constants, seat belt wear, filtering performance, oil pressure, steering fluid pressure, bearing temperatures, hydraulic pressure to the transmission valve bodies...somewhere there's a deficiency from stock....but you don't want to do that nor would you make any decisions based on it unless there was an actual problem. i view this in a similar light, it's the same thing just Subaru chooses what is being monitored, how, and why.

 

if it makes you feel better, then tear it up, your confidence in the car will pay off in the long run more than likely.

[StructEngineer]

Have you checked for exhaust leaks upstream from the cats? You'd be surprised how many people get 4020 issues only to due to leaking exhaust joints. This keeps the cat from operating at the correct temperature.

[GeneralDisorder]

I know the anti-foulers make the car think that everything is working properly, but it's not. I would prefer to fix the problem as opposed to working around it.

 

I think your mistake is in *thinking* that you have a problem. What you have is government meddling taking a bite out of your wallet. Good god man - don't they already take enough from you in taxes!?!?

 

That is the same level of thinking that causes the elderly to conclude that a good way to spend their social security check is to feed it into the slot machines on the Indian reservations .

 

If you just open your mind a bit you will find that the non-foulers, or the 02 sensor simulator products really *are* fixing the problem . Punch the cat's out completely so there's no chance of them clogging and you have "completely fixed" the problem .

 

At the end of the day - it's a sub-routine in the computer that's looking for a signal from a sensor that is within a specified tollerance range. It is mandated by the governement. That sensor has absolutely nothing to do with engine management from a mileage or fuel/ignition mapping perspective. Any information that could be gathered from the exhaust stream and used for tuning purposes has been destroyed by the function of the catalytic converter. The non-fouler or similulator is simply giving the software the signal it wants to see to not throw the code. No more, no less. Solutions can range from replacing all the sensors and the converter and sealing up the exhaust, to reprogramming the ECU, to the non-fouler or the simulator. They are all viable, 100% effective "fixes" to the immediate problem of the code and the CEL. Period, end of story.

 

GD

Edited April 29, 2010 by GeneralDisorder

[nipper]

before we go anywhere, who made these "cheap cats" . I have a feeling i know and that can be the source of the entire issue. Have you replaced the cheap cats with a better one?

 

When the cats run hotter then designed you are not buring anything off. You are melting the catalyst.

[Fairtax4me]

If I could make the cats hotter, would I, in theory, burn off more crud?

No, You'd be more likely to start a fire.

 

The catalytic converter doesn't "burn" "crud". It changes the chemical composition of the exhaust gases leaving the engine, into different gases that are more pleasant for the environment. It does this through heat and a reaction with the catalyst material used in the converter (mostly platinum).

 

hmmm? A cheap easy experiment. I like it! Burn more stuff, leave less for the cats.

 

What's the down side to a hotter plug?

 

A "hotter" plug won't burn more "crud" either. Hot vs cold in spark plugs is the plugs ability to transfer the heat that builds up in the plug into the cylinder head. A hot plug simply doesn't transfer heat as quickly as a cold plug. It has nothing to do with the temperature of the spark or the temperature of the combustion. With a hotter plug the engine is more likely to ping which will cause the ECU to enrich the A/F mixture, if it can't get rid of the ping through retarding the spark timing. Both of which will lose power and lower fuel efficiency, further complicating your perceived P0420 problem.

[charm]

The cats are Bosals.

 

As an environmental scientist and a former southern Californian, I have seen the impacts that smog equipment has had. I recall, as a kid in the early 80's how much the air would sting my eyes. That's gone away. Why? Largely smog equipment.

 

The Subaru motors, as I understand it, do run pretty clean, but the cats are still doing something.

 

The concern is that there is more pollutant entering the catalyst then the catalyst can handle. The reprogramming or, in the case of my car, the anti-foulers are telling the computer that the catalyst is doing its job...it's not. What I want to know is why are the cats not handling the pollutant levels. For this thread, this question is rhetorical since it's been talked to death on this forum.

 

For now, I'm not going to change a thing. I'm not worried about the reliability of my car. But I do want things to operate as they're intended. If I'm using antifoulers, reprogramming the ECU, using hotter plugs, etc. then things are not operating as designed.

[johnceggleston]

For now, I'm not going to change a thing. I'm not worried about the reliability of my car. But I do want things to operate as they're intended. If I'm using antifoulers, reprogramming the ECU, using hotter plugs, etc. then things are not operating as designed.

 

 

it sounds like you need to visit a shop that can analyze your exhaust gasses so you will know. then you can make an informed decision.

[nipper]

Darn i was going to guess Eastern.

 

I agree with above, shop that is good at this kind of thing, as not all shops are.

 

nipper

[GeneralDisorder]

For now, I'm not going to change a thing. I'm not worried about the reliability of my car. But I do want things to operate as they're intended. If I'm using antifoulers, reprogramming the ECU, using hotter plugs, etc. then things are not operating as designed.

 

The "design" is created by a man. Men are fallable.

 

"operate as intended" assumes that there is someone other than you that controls the "intended" operation. It is not so. YOU control how it's "intended" to run as it is now your intention - if you stick with how it was designed your intention is to burn money and time and gain nothing. I submit that a better intention is to change the design to your needs.

 

Open your mind to the greater possibilities of controlling your environment how you see fit. That is the greatest freedom a man can have and the spirit of America. Love it. Live it.

 

Smog laws are fine. But the majority of cars on the road are less than 10 years old and under some kind of warantee. Let the numbers game win this one. Your personal battle with a single catalytic converter is less than nothing in the fight against smog. You care too much to see the forest for the trees my friend. Step back and get some perspective. Go for the big wins - don't waste time and resources on trivial problems that at the end of the day will only make you feel better because of unreasonably held beliefs that one man's car will make some kind of difference.

 

GD

[nipper]

i don't see anything listed about a valve adjustment, tuneup. Have you taken a vacum gauge to the engine to see how it is running internally. Sort of everything you have thrown at it is like cutting off your foot for an ingrown toe-nail.

 

You need to get the car back to the way it was originally (aside from the cat for now) to really do a good diagnoses.

[Fairtax4me]

Here are a few other tricks about the P0420 code.

 

P0420 is Catalyst efficiency below threshold. But what determines the catalyst's "efficiency"? Well the cars Electronic/Engine Control Module (ECU) receives a signal from two oxygen sensors (or more depending on the vehicle), one before and one after the catalytic converter(s). It compares the values of these two signals and based on a preset graph determines if they are within a certain specified range. If the values of these signals falls outside the acceptable range, the ECU determines that there must be a problem with the catalyst, stores a code, and illuminates the MIL. (malfunction indicator lamp, aka check engine light)

 

What is the problem with the catalyst? Usually it's clogged and can no longer fully process the amount of exhaust gas entering the catalytic converter. There can be several reasons for this. Usually because the converter is old and is just "used up". But it may have been damaged by driving while the engine was misfiring, allowing raw fuel into the cat will cause it to overheat and melt. It could be oil contaminated due to piston ring damage, worn valve stem seals, or worn Turbo bearings/seals allowing oil into the exhaust stream. Driving with a bad O2 sensor can also ruin the converter much the same way as driving with a misfire.

 

The cure here is to replace the damaged or old converter with a new one, which you have done, yet it has not cured the perceived problem that is being detected by the ECU. So why has it not cured the problem? Well probably because the converter wasn't the problem in the first place. A new after market converter has to stand up to the same "cleaning" standards as a new OE converter, otherwise the EPA won't allow it to be sold. So ,for a short time at least, the after market converter should do just as or nearly as good a job of converting harmful exhaust gases into less harmful forms as the original unit. The difference is in how long the converter lasts. An after market unit is designed to last maybe 3 - 5 years, whereas the OEM unit has to last at least 8 years. The EPA warrants catalytic converters supplied on new vehicles for 8 years or 80,000 miles. So it is to the manufacturers advantage to use high quality components that will last at least that long or in many cases longer. Especially in the case of certain manufacturers who offer 100k mile warranty periods on their new or certified used vehicles.

 

If it's not the converters fault what is it? Just because the ECU finds a problem, doesn't mean it always finds it in the right place. There are plenty of cases where this code has been set because of a failing O2 sensor, either upstream or downstream. (which you've replaced both of) Or because of another problem that the ECU hasn't yet detected. The EGR valve for example, one that is partially stuck open when it is supposed to be closed, yet still moves freely when the ECU tells it to. The ECU may not be able to detect the problem, but it presents an opportunity for air to leak into the exhaust stream which can effect the signal of the upstream O2 sensor just enough that it reads a lean condition. This tells the ECU to add more fuel to the mixture to prevent combustion temperatures from getting too high.

 

This can also be caused by exhaust leaks before the upstream O2 sensor, usually at the cylinder head or at the weld where the pipes come together. It could also be a pinhole behind a heat shield that is not visible, and can't yet be heard. Or it may be a leak right around the O2 sensor itself.

 

Problems can also be caused by vacuum leaks. If there is a leak between the manifold and cylinder head next to just one of the intake ports the mixture for just that cylinder can be throw off. The ECU has no way to detect, nor correct this unless it gets so bad that a misfire occurs. But before it gets to that point the O2 sensor will start to read that the mixture is lean. The ECU will detect changes in the mixture between cylinders at low RPM when the exhaust is moving fairly slowly. But it generally sees this rich lean rich lean back and forth "swinging" as normal operation because no two cylinders burn the mixture exactly the same. At some point it will read that there is a problem with the mixture and will start to richen to correct the lean part of these "swings". But the problem is, now the downstream O2 sensor starts seeing a lower oxygen content due to the extra fuel being added to correct the swing. Rather than blame itself (for a reason it can't detect), the ECU determines that the catalytic converter must not be doing it's job, and it sets a code... P0420. Meanwhile there is nothing wrong with the catalyst, or the O2 sensors, it's just an air leak confusing the computer.

[Olnick]

Nice explanation, Fairtax. Thanks.

[nipper]

Yes what Farifax said

[lucid_door]

I remember doing ECU reprograms on tons of Buick/Olds/Pontiacs that would set an EGR code. GM determined that while installing a new valve would fix the code, their tolerances were too tight and the slightest film of buildup would cause another code to set even with the new valve. So we reprogrammed looser tolerances in for the EGR system. Same type of scenario; not really a malfunction as far as malfunctions go, just settings so strict it didn't allow for any real world usage.

[charm]

Vacuum looked good a couple months ago, haven't checked since. Valves were adjusted and looked great 40k miles ago with the head gasket replacement (the start of the bad catalytic converter problem). So the EGR? How do I inspect, clean, adjust the EGR? Or should I just replace it and be done with it? Air leaks have been looked for several time by me and 3 different mechanics and not found. I feel pretty confident that after 6+ air leak searches that my exhaust is sealed up pretty tight. Admittedly, the tolerances in the ECU are probably to tight, but they are the existing tolerences. Until they change, and I am the last person who should be changing them, those are the parameters which dictate whether or not the car is operating as designed. Give me a 1960 Chevy with a small block V8 and I'll tweak it until the cows come home. My confidence with that is higher because there's no ECU. The mechanicals are straight forward and obvious to me. The Subaru, while straight forward for a modern car, still requires way too many wires. As far as the environmental damage from 1 car, you're right, 1 car won't make a difference. 1 person duming oil into a storm drain won't make a difference. 1 person tossing a cigarette out their window won't make a difference. 1 person not recycling won't make a difference. But there are a lot of people. If each person does a little, a huge difference can be made. Imagine if we all stopped driving our cars. I know, I'm not about to do that either. But what if? What if we reduced our dependance on oil, foreign and domestic? What would happen to the wars in the Middle East? Would we be dealing with a massive natural disaster in the Gulf? You suggest I not worry about my 1 car with a bad catalyst because it's just 1 car. Well, it all adds up. I won't worry about your car, that's your responsibility. My car is mine and I intend to do the right thing. If you choose otherwise, well, that's just job security for me. Keeping harming that environment and make sure I have a career until the day I die.

[idosubaru]

EGR's they're easy to clean, just remove and spray it out. or buy a new one, very easy to replace, somewhere around $100-$150 for the valve and a new gasket. that's not going to fix your O2 issue, though.

 

new Subaru converters will most likely do what you're looking for, is there a reason not to go that route? I'm guessing cost but you sound eager to be done with it? Are those old converters under warranty, return them?

 

The EGR scenario was an analogy, not a fix to your problem. The one car not saving the planet also was an analogy, not about how polluting is okay. Analogy is a communication technique. The black and white rendering of everything is not helping you.

 

The carbon footprint of efforts to address this is probably more than the zero or negligible impact of your current set up. It's likely that this makes the environment worse by trying to fix it but at the gain of feeling better about it. Your earlier suggestion holds here - one person...but if everyone replaces benign parts: generating more trash, transport, fuel, costs, storage, delivery, maintenance, electricity etc. We are right back where we started - the system is inefficient and wise people that can grasp the big picture see that. It shouldn't be this hard to say "the government is inefficient", I think I hear people complain about that every day. :lol:

 

Good luck, hope you find a way to move on from this issue.

[GeneralDisorder]

The Subaru, while straight forward for a modern car, still requires way too many wires.

 

Actually it's a very simple system. Trust me - I've rebuilt Quadrajet's and the Subaru MPFI system is a lot more simple and straightforward than the black-magic that goes on inside a late-70's to late-80's carberetor. And at the end of the day a lot more effecient and controllable.

 

Plus - the ECU is self-diagnostic. It tells you if something is wrong. In this case it's just too sensitive.

 

As far as the environmental damage from 1 car, you're right, 1 car won't make a difference. 1 person duming oil into a storm drain won't make a difference. 1 person tossing a cigarette out their window won't make a difference. 1 person not recycling won't make a difference. But there are a lot of people. If each person does a little, a huge difference can be made. Imagine if we all stopped driving our cars. I know, I'm not about to do that either. But what if? What if we reduced our dependance on oil, foreign and domestic? What would happen to the wars in the Middle East? Would we be dealing with a massive natural disaster in the Gulf? You suggest I not worry about my 1 car with a bad catalyst because it's just 1 car. Well, it all adds up. I won't worry about your car, that's your responsibility. My car is mine and I intend to do the right thing. If you choose otherwise, well, that's just job security for me. Keeping harming that environment and make sure I have a career until the day I die.

 

The point (which you are missing) is that the catalytic converter is still in place, and still doing it's job. The computer is sensitive to small changes and as such the effeciency it see's has tripped it's sensitive alarm. That does NOT mean it isn't still doing a pretty good job of eliminating emissions. You are doing a lot of hand-wringing and sweating about something that we have been trying to make you understand is too sensitive and likely means almost nothing in real-world terms. If you actually put a gas analyizer up the tail-pipe then you would know what you are dealing with here. It's a matter of a few hundred parts per million (PPM) that is tripping the alarm. Without the cat, you would be looking at THOUSANDS more PPM. The difference is gigantic. You have replaced the cat - so you know it's good. You have done all you need to do. Now it's time to let it go and feel good about your efforts.

 

You also don't seem to understand that this is a numbers game and it's about all those people out there that aren't going to know how or understand the non-fouler trick. They are going to bite the huge bill and replace all the components with OEM to get rid of the light. You are very fortunate to be of above-average intelligence and have come here to get the real answers - which we have been paitently giving you despite your tendancy to want to be a mindless consumer.

 

GD

[schlit]

After reading through all the posts I think the only one missing something is you. I find that people who pollute look for any and every excuse to do so.

 

How can you judge that the limit is too harsh?

[idosubaru]

Man this is a contentious topic. Too close to politics or something I guess?

 

How can you judge that the limit is too harsh?

You might not pass your own standards in regards to your own question. You belittled and judged him...based on....how can you call him "missing something", why did you completely miss his point? You are missing the discussion completely, this has nothing to do with GD polluting. Communication 101 people - analogy, metaphor, please work with us here and have some level headed discussion, it might require some high level reading though!

 

One way to be quantitative is for folks familiar with Emissions testing states where you see that older Subaru's (or other cars) have essentially the same emissions as newer ones. Even though they're not crapping out about O2 sensors all the time - older Soobs only have 1 O2 sensor, newer ones have a system of 2 and even 3 O2 sensors.....but no lower emissions, the catalyst is still working the same in the converter. They can have the same emissions levels with the Check Engine Light on. That light does not mean you're polluting. That's not how it works.

[GeneralDisorder]

How can you judge that the limit is too harsh?

 

^ mindless consumer mentality ^. The "man" claims it is so and has put it out on Power-Point. Thus making it true!

 

Someone has to. You gonna do it for us? .

 

94 posts and he's telling me how it is!...... Tell me "shlit" (was the 'l' an accident?) - how many of these codes have you fixed?

 

And for the reccord I never said the "limit" was too harsh. I said the tollerance for the sensor is too narrow. There is a big difference as pointed out by Gary. I have Subaru's that are 25+ years old with the original cat that pass a tail-pipe examination without trouble. They don't even have O2 sensors.

 

You might not pass your own standards in regards to your own question.

 

I'm thinking along those lines myself Gary.

 

GD

Edited May 16, 2010 by GeneralDisorder

[99ImprezaOSport]

Romper, bomper, stomper boo. Tell me, tell me, tell me, do. Magic Mirror, tell me today, have all my friends had fun at play?

 

WOW, What interesting, informative, and general environmental trip it's been. I see a lot of regular, helpful, folks posting here (GD, Nipper, gross, fairtax, johnc, etc...) and would just like to add my 2cents from my experiences.

 

As for the Cat problem... I like many others have purchased an aftermarket Cat, but unlike some, I only purchased ONE which I ended up recycling on ebay. So an aftermarket Cat and 2 o2 sensors my problem was not fixed. I purchased a new factory Cat and even with the 2 aftermarket o2 sensors the problem was and still is fixed, 3 yrs and counting.

 

I have to a agree...

Your earlier suggestion holds here - one person...but if everyone replaces benign parts: generating more trash, transport, fuel, costs, storage, delivery, maintenance, electricity etc. We are right back where we started - the system is inefficient and wise people that can grasp the big picture see that. It shouldn't be this hard to say "the government is inefficient", I think I hear people complain about that every day. :lol:

 

Good luck, hope you find a way to move on from this issue.

 

Toying around trying to correct a problem with aftermarket parts, which we can see is not fixing the problem, perhaps is not a good environmental decision. Even using "anti-foulers" is not a good environmental decision but perhaps passes the ECU and the government emissions, as long as the inspector misses "The beeyootiful SHINY button! The jolly CANDY-LIKE button!" which pops the o2 out.

 

Speaking on the environment, how about this one... during the day, instead of keeping your headlights on, which generate a ton of heat, leave them off until the light of day leaves us until tomorrow. How much heat is generated every day from people that keep thier headlights on?

Edited May 16, 2010 by 99ImprezaOSport