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What's the best replacement to get? I have been told to replace mine after 90K. I am registered and inspected in Vermont.

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your CAT should last as long as your vehicle.

The O2 sensor does "wear out".. I had to replace mine at 42000 miles - 17 years. I was getting a check engine light - code 20.

If your CAT goes bad, there is a reason and that reason would need to be addressed. They rarely do.

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Yeah I have never heard of replacing a Cat just for the hell of it. Couldn't find any references online of any interval for doing that either. I hate it when mechanics just think of ways to spend your money. Make him show you in the factory service manual where it says to do that. When he can't give him a talking to but make sure there are lots of other customers around

Linda S

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We used to replace many cats at fairly early miles. Never just for the heck of it, though. Many early cats would plug and when they did -a simple vacuum test would show the cat was plugged and needed to be "replaced." They would often smell like rotten eggs when plugged. Truth is - with many - we just eliminated them. My Datsun 280Z got a plugged cat and I just hollowed it out and removed all the honeycomb stuff inside. I suspect cat-plugging used to be more common due to the quality of gasoline at the time. And that keeps changing and changing. Soon the USA will be switching to "ultra-low sulfur" gasoline, just like was done a few years back with diesel fuel.

Many ads years ago would promote cat "test pipes." These were pipes made to eliminate the cat but since doing so was sort of a crime - they called them "test pipes."

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Cats do go bad but usually for a reason. With the V6 it is possible that antifreeze from a leaking head gasket would damage it and certain silicone sealants used on valve covers etc. could also do damage. Mechanical damage could be a factor they do come loose inside some times. It is not unknown for them to just fail. But unless they are causing problems chances are pretty high they will outlast the engine. Any garage worth their salt can usually determine a plugged cat with a simple vacuum gauge. At least with modern vehicles they fall under the factory emission warranty of 80,000 miles so they expect them to last at least that long.

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Cats serve a purpose I would suggest you leave them in place they are a device that cuts pollution significantly and I would request that you do not pollute my air if you wish to do so do it in your own garage.

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Cats serve a purpose I would suggest you leave them in place they are a device that cuts pollution significantly and I would request that you do not pollute my air if you wish to do so do it in your own garage.

So going by that reasoning - I guess you don't want anyone driving their non-cat vehicles anywhere? Even if built that way new and legal? Like my 1978 Toyota Chinook? I'll drive anywhere I please. Air-travel via diesel fueled jet engines is the #1 polluter of our atmosphere. The little bit of emissions a car or truck can make compared to air-travel is less then a "drop in a bucket." To go even further - how much total energy is wasted and how much extra pollution is caused by the "new car and truck" market?

I also assume your take on things means all auto racing anywhere in the world be banned?

Just my personal point of view. I'll restrain myself to just running my non-cat stuff in "my garage" when people stop flying all over the planet on a whim - in big jets with super high emissions.

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My 1974 Datsun B-210 had the cat replaced twice because it failed the Ca. smog test. Never used nor leaked any oil or antifreeze and always ran the same (great :) ) during the many years I owned it.

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jd, I do agree with Maineah, to the point that if it had one, it should keep one. A high flow cat does not cost any measureable amount of power, and cuts a significant amount of emissions. Again, IF IT HAD ONE. I have a '78 Celica that is a "non-catalyst" car, so don't plan on adding one. I have a friend who has one as well, but could not get it to run clean enough to pass Oregon's sniffer only emissions testing. It then passed with flying colors.

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That's fine with me. We all cannot agree with everyone, all the time. For me - I'll drive my rigs where ever I want. I don't have anything anymore that is "missing" a converter though. My 1978 Toyota Chinook never had one. Never had to touch the cats in my newer rigs. They usually have high stainless-steel content and don't rot out like the rest of the exhaust systems often do.

I sold my 1979 Datsun 280ZX last year. I had driven it for many years with a hollowed out cat. The reason being it plugged and a replacement was very expensive for that vehicle at the time it plugged (around 1982). That car put out less emissions then most cars of the time with NO cat. Besides it was a special low output California-only car and I owned it in New York. So yeah, I drove it and would not "keep it in my garage" to make someone like Mr. Maine happy.

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So going by that reasoning - I guess you don't want anyone driving their non-cat vehicles anywhere? Even if built that way new and legal? Like my 1978 Toyota Chinook? I'll drive anywhere I please. Air-travel via diesel fueled jet engines is the #1 polluter of our atmosphere. The little bit of emissions a car or truck can make compared to air-travel is less then a "drop in a bucket." To go even further - how much total energy is wasted and how much extra pollution is caused by the "new car and truck" market?

I also assume your take on things means all auto racing anywhere in the world be banned?

Just my personal point of view. I'll restrain myself to just running my non-cat stuff in "my garage" when people stop flying all over the planet on a whim - in big jets with super high emissions.

Auto racing does not involve million of cars aircraft hold 200 or more people that would be driving hundreds of miles other wise and they were the first transport with catalytic converters.

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jd, I do agree with Maineah, to the point that if it had one, it should keep one. A high flow cat does not cost any measureable amount of power, and cuts a significant amount of emissions. Again, IF IT HAD ONE. I have a '78 Celica that is a "non-catalyst" car, so don't plan on adding one. I have a friend who has one as well, but could not get it to run clean enough to pass Oregon's sniffer only emissions testing. It then passed with flying colors.

Yes because it was grandfathered the emission tests reflect the fact that they are only as good as when they were built they can't do any better.

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Though I don't own a plane, I do have 3 chainsaws, 2 generators, 2 lawnmowers, 3 snowblowers, a leafblower and an edge trimmer. No catalytic converters on any of them. :)

Do you run them all at once? I guess my point if it has it leave it.

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1. no reason to replace it if it isn't clogged and no CEL. what might need to be replaced is your mechanic....??

2. some of the Detroit iron guys run cats on 500+hp motors....ie, the modern high flow cats are pretty free flowing and won't cost you significant hp

3. yes, it IS possible to improve things (emissions, throttle response, part throttle hp) over factory on many carbureted 70s vehicles, if you're willing to drop the big $ that you won't get back if you sell it. many folks in Brit sports cars have swapped in TBI systems for the old dual SUs or Stromberg(s); i'll guarantee their tailpipe #s would be better than stock, esp if they add a cat while they're at it. ditto for the guys in old BMWs who have swapped in EFI from newer bimmers to replace the solex(es).

practical? no. but i'll bet those guys don;'t love their 2002s and MGBs any more, or plan to keep em any longer, than this crowd plans to keep their Toyhomes.....

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Auto racing does not involve million of cars aircraft hold 200 or more people that would be driving hundreds of miles other wise and they were the first transport with catalytic converters.

I don't involve "millions of cars" either. So if they can race their MANY cars and you think that is OK, why cannot I drive one of mine? Hey, I'll even let people watch me drive for free and no need to buy expensive tickets.

As to air/jet travel? Hogwash. Many people who fly all over the world on a whim would likely NOT go the same places by boat or car unless it was REAL important.

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A whim? Doubtful because of the huge numbers. Millions of cars few race cars and only on weekends I did not say I liked the ideal but it is tolerable due to the insignificant numbers.

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Good golly, give me a break. People fly all over world to places they'd never consider going to if not for jet travel. So yeah, I call that a whim although many consider it some sort of entitlement. I guess I'm lucky since I've only flown in small military planes. Other then that - never flown anywhere and never will. If I can't drive there - I figure I don't need to go there so bad.

I wonder how much non-renewable energy was just wasted by all the "experts" who flew big jets to the global warming summit? And how much pollution was made?

I know that for me and my family - our lifestyles have very low impact on the environment. A heck of a lot lower the most people. In light of that - excuse me for not feeling guilty for driving a 40 year old vehicle once in awhile that has no cat.

Did you ever stop to consider how much energy is wasted and now much pollution is created - just in the creation, building, and then destruction - of a new car? Driving something old and keeping it going - can just in that aspect - save a lot of energy.

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I live in Maine most of my family lives in Maryland it's close to 600 miles one way and 10+ hours of driving my truck would burn around 55 gallons of gasoline I like most other people that are flying find it to be the best possible way to get where we are going and the most efficient. I fully remember the "test pipes" they were installed mostly because of ignorance and resistance to change even though it was to their benefit to leave them in place. If you drive around in a car old enough not to have a cat that is the way it is because that is the way it was built but removing one out of ignorance effects more than just the owner.

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The "test pipes" weren't just about ignorance. Early cats often had plugging problems. And - since there was no Internet to go out and comparison-shop, prices were at times crazy. I remember many a cat back in the 70s that cost near $300 and sometimes the whole damn car only cost $200.

And about air-travel. I don't complain about it on a routine basis, nor do I condemn people for using it. My meaning of "legitimate" being having a good reason for the trip and air-flight being the most cost-effective. I suspect the vast minority of air travelers do not have "legtimate" reasons by my def.

Kind of reminds me when my boss - back in the 70s - insisted I fly to Iowa and stay for a week-long John Deere training seminar. I refused. I told him I could sit home and study a few tech manuals and learn more in less then one day - then I could learn spending a week in Iowa and making two Jet trips.

I proved to him I was correct. I won the John Deere "Golden Belt-Buckle" award that year for taking 1st place in their tech certification tests.

Back to the recent "Global Warming" summit. How many world "leaders" flew there in huge jets just to sit around and blow hot air? Even if anyone had something worthwhile to share -with today's tech - it could of been done by digital video conferencing. Another prime example of fuel waste and un-needed pollution made.

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