Is it a bad idea & illegal to remove the catalytic converter?

[steve_spackman]

A friend of mine had her catalytic converter taken off her car. I was wondering if this is allowed?

[Mark]

It would almost certainly void the warranty and fail an MOT.

[steve_spackman]

A friend of mine had her catalytic converter taken off her car. I was wondering if this is allowed?

Sorry for any confusion, but this is a question for the North American guys. I've heard that it is illegal in certain states for a car not to have the converter. And also does it decrease MPGs?

The situation is that the car wasn't working right, kept stalling. So the car was taken to the shop and the guy took the converter out thinking that was going to fix the problem. However, the car started acting the same way as before, and took it back. Came to realise that it was the fuel pump instead. He replaced the fuel pump and now the check engine light is back on. I was wondering if it had ANYTHING to do with the removal of the coverter.

Thanks for any feedback.

[anthonyvop]

Back when they 1st started it made good sense to remove that Cat.

Now with computerized engine management system it will decrease performance unless you re-map the EMS.

And yes it will void the warranty and technically against the law.
States like California enforce it.
States like Florida could car less.

[Kneeslider]

And also does it decrease MPGs?



Somewhat paradoxically, if you put a Catalytic converter on a car, the MPG will go down. So what the catalytic converter is doing is decreasing the concentration of pollutants in the exhaust, but it does have the effect of creating a restriction within the exhaust, which costs you some efficiency.

Another effect of the cat is that the engine needs to run at the optimal stochiometric point of 14.7:1 air to fuel ratio, otherwise the unburned hydrocarbons (if the mixture is rich) will 'poison' the cat, and if the engine is too lean the exhaust gas temperatures can be too high for the cat to tolerate. For this reason, all engines fitted with catalytic converters need to have Electronic Fuel Injection systems which can deliver the optimal ratio throughout all conditions of rpm, throttle opening and load. The cat effectively killed off carburettor technology.

Some people may argue that a 'lean burn' engine which operates at over 14.7:1, is more fuel efficient, but puts out greater concentrations of pollutants. Racing engines tuned for optimal power and efficiency often run in a lean burn configuration.

So the paradox is that to save the planet, you have to burn more fuel.

[Hondo]

The converter is required to be installed in Louisiana. It's physical presence is checked during the annual inspection. On vehicles that still use, or have a carb installed, it's not unusual for the converter to be gutted out inside while looking intact from the outside. Not legal, but this is Louisiana.

[Magnus]

From my pow it sounds like as you have a broken lambda-meter

[leopard]

Let alone if you know that doing so is against the law I'd suggest not to get rid of anything useful like the cat.

[SportscarBruce]

Back when they 1st started it made good sense to remove that Cat.

Now with computerized engine management system it will decrease performance unless you re-map the EMS.

And yes it will void the warranty and technically against the law.
States like California enforce it.
States like Florida could car less.

^ I fully support what he said, but there's a slight technical correction to be made. Only if the car is equipped with a post-cat O2 sensor will the EMS revert to a limp-home fuel/ign map. However, on a street car removing a modern, honeycomb mesh cat makes no sense because it's hardly a bottleneck, as was the case with early platinum-coated pellet design. OTOH the post-cat exhaust on OEMs are usually full of price-point compromised mashed bends. Interestingly, I once installed full-length stainless headers on a 2002 GTO without touching the necked down exhaust system and it dyno'd a good 30 hp improvement. Maybe due to stainless steel's heat conduction qualities the gasses sufficiently cooled to the point of making the OEM exhaust an asset, or at least not a factor?

[MrJan]

It would almost certainly void the warranty and fail an MOT.

Nope. Cars registered before August 1992 do not have to meet such stringent emissions regulations and subsequently don't have to have a Cat. I know this because I was considering getting a de-cat for my car but it was registered in October '92 so just misses out :( There are also a lot of people who fit the Cat just for the MOT and then change it back over, although obviously this means it would fail emissions tests and voids MOT, insurance and is properly illegal :)

http://www.jap-spec-performance.co.uk/mr2/faq.html

[SportscarBruce]

A little o/t but if anyone here has a old v8 car of little collector value and you're in the market for a new car KEEP IT REGISTERED AND DON'T GET RID OF IT! Clunker bill is on the way. Last year I passed up a practically free 1982 Oldmobile. :(

[Mark]

A little o/t but if anyone here has a old v8 car of little collector value and you're in the market for a new car KEEP IT REGISTERED AND DON'T GET RID OF IT! Clunker bill is on the way. Last year I passed up a practically free 1982 Oldmobile. :(

Already in place in the UK. Daniel has already got £2,000 for a very old car traded in for a brand new one. A few people I know are looking at buying a new car too now.

[Daniel]

Already in place in the UK. Daniel has already got £2,000 for a very old car traded in for a brand new one. A few people I know are looking at buying a new car too now.
My car isn't/wasn't that old! My 406 is an early 1998 car :p I would say that's not old.

As for the problem the OP has I'd put money on the check engine light being on because it has a post cat O2 sensor and it's throwing up a message because there's no cat there.

[Magnus]

Nope. Cars registered before August 1992 do not have to meet such stringent emissions regulations and subsequently don't have to have a Cat. I know this because I was considering getting a de-cat for my car but it was registered in October '92 so just misses out :( There are also a lot of people who fit the Cat just for the MOT and then change it back over, although obviously this means it would fail emissions tests and voids MOT, insurance and is properly illegal :)

http://www.jap-spec-performance.co.uk/mr2/faq.html

Didn´t know... In Sweden it´s from 88. I more emant that if the enginelamp lits, it could be because of faulty lambdameter, generally speaking

[JSH]

Sorry for any confusion, but this is a question for the North American guys. I've heard that it is illegal in certain states for a car not to have the converter. And also does it decrease MPGs?

The situation is that the car wasn't working right, kept stalling. So the car was taken to the shop and the guy took the converter out thinking that was going to fix the problem. However, the car started acting the same way as before, and took it back. Came to realise that it was the fuel pump instead. He replaced the fuel pump and now the check engine light is back on. I was wondering if it had ANYTHING to do with the removal of the coverter.

Thanks for any feedback.

Ignoring the fact that any half decent mechanic would check the fuel pump before tearing out the catalyst..... :confused:

Yes, removing the cat probably has resulted in the MIL lamp coming on.

[SportscarBruce]

Have your friend go down to the auto parts store, ask them to plug in a scanner, and post the diagnostic trouble codes here along with year, make, and model. :)

[steve_spackman]

Have your friend go down to the auto parts store, ask them to plug in a scanner, and post the diagnostic trouble codes here along with year, make, and model. :)

She went to the local auto parts store..they did the diagnostic. The guy said that the reason is that the guy who worked on it never replaced the CAT. He said that by law a car shop has to replace it if he removes it.

Its a 2003 Chevy Cavalier coupe

[SportscarBruce]

If you don't mind ask her if the repair bill shows a four-digit DTC code of some kind in the narrative. Some shops forward along the mechanic's notes, but not all. Hopefully this one does. The engine model or at least displacement in liters will also help.

[Mark in Oshawa]

The mechanic who did this is a BUTCHER. Any mechanic with half a brain would NEVER touch the Cat. Any misfire or stumbling usually is a computer issue having to do with the fuel metering. It is either running rich or the timing is out, and with all the electronics on modern cars and that Cavalier in particular, it should have been caught with a plug into the car's OBD.

In short, she should report this guy to the state for masquerading as a mechanic because it is obvious he is clueless and at the very least, she should stop giving this guy money once he puts the Cat back on at his expense.

If this was Canada, there would be hell to pay. It is part of our certification when the car changes hands that the Cat is there. I also know the car is designed to run with that thing there so removing it just adds problems, not solves them. That, and the car in Ontario and most of the bigger provinces has to pass a tailpipe emissions test once every two years and I can guess that without it, it would NOT pass.....

[steve_spackman]

The mechanic who did this is a BUTCHER. Any mechanic with half a brain would NEVER touch the Cat. Any misfire or stumbling usually is a computer issue having to do with the fuel metering. It is either running rich or the timing is out, and with all the electronics on modern cars and that Cavalier in particular, it should have been caught with a plug into the car's OBD.

In short, she should report this guy to the state for masquerading as a mechanic because it is obvious he is clueless and at the very least, she should stop giving this guy money once he puts the Cat back on at his expense.

The 'mechanic' never put the CAT back on her car. Her mpg has decreased and the car sounds and smells bloody awful

[Dave B]

You should give the mechanic's contact details to Ripley's Believe It Or Not exhibition.

They'd love to have a fully-functioning human being with an IQ in single figures.

[schmenke]

...Its a 2003 Chevy Cavalier coupe

Well, there's first problem... :p :

[steve_spackman]

Well, there's first problem... :p :

;)

[Jag_Warrior]

A friend of mine had her catalytic converter taken off her car. I was wondering if this is allowed?

If it's a car for off-road use only (read, racing), then no, it doesn't have to have a cat. The series you race in might require it, but the government won't care. An engine tuner worth his salt can tune to any exhaust or intake modification - assuming it's right for that engine. My car is specifically tuned to the aftermarket intake components and exhaust system that I have. With the mods, but without the tuning, I would have probably toasted my engine a long time ago. But if it's for on-road use, then yes, it's a federal law - a more lax state law wouldn't matter. Not only is the cat(s) not supposed to be removed, it's not even supposed to be replaced unless the existing unit is damaged or defective.

I'm not aware of any individuals getting into (federal) trouble for removing a cat - although I know a lot of people who have been locally popped for loud exhausts. But I do know of two exhaust shops, that also did state inspections, that had their licenses yanked and got a call from some feds, out of the EPA I believe. And I think Midas also got into a lot of trouble a few years ago over this.

2003 Chevy Cavalier? Get full coverage and burn it for the insurance. :D

[Azumanga Davo]

But the Cavvy is so much faster now, am I right?

http://image46.webshots.com/46/6/69/1/336266901NqUUHc_ph.jpg
I see what you mean about extra pollutants now though... :D