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What's the harm to cut converter off 2004 Saab 9-3?

Would it harm or hurt in any way to cut my converter off my 04 saab 93 2.0 turbo?

It would harm the air you and I breathe, open yourself up to a federal charge of tampering with emissions equipment and finally set a check engine light that will never go away.

Otherwise, no.


LOL… In addition to all the salient points Mustangman just made… Why are you thinking about doing this anyway… Cats rarely go bad in my experience…and I mean very rarely. Is there a code you are getting that makes you think the cat needs to go or is it damaged physically? A P0420 code (Catalytic efficiency below threshold) is very common and is most often resolved by O2 sensors and or fixing any exhaust leaks you may have for example…

Just curious if some code is pushing you toward this bad decision or not


And the computer system that runs the car expects the cat/o2 sensor to work. Removing the cat would screw that (and us) up.


Well, it’s also gonna make it loud as hell unless you weld in a straight pipe, and unless you’re doing this for a race car that will never be driven on the street, as @Mustangman said, you’ll be breaking the law, and the noise you’re making is going to clue every cop within 5 blocks as to what you did.

By the way, removing the cat isn’t going to give you appreciable gains in performance, so if that’s the motivation, law and morality aside, don’t bother.


I am going to make a guess that Adam is about 17 to 22 years old, wants to “straight pipe” his 9-3 so it makes “mad power” 'cause he thinks that cat is just robbing his turbo… And it will make it sound really cool, too! :roll_eyes:

The major harm is to the environment. And if you get caught - it could cost you a lot of money.

There are ways to do it. You have to trick out the ECU that the cat is gone. If you don’t do that, then the car will perform like crap and gas mileage will plummet. It’s not worth it.

We still do not know the actual reason for Adam to think about “de-cating” his car…
If this is something like P0420 code, then replacing the front converter is what is needed to “make it right”.
Aftermarket converter is around $250:,2004,9-3,2.0l+l4+turbocharged,1428612,exhaust+&+emission,catalytic+converter,5808
This is “direct fit”, so even with all the bolts frozen and in need of “advanced techniques” to remove, should not take more than 2-3 hours of work for DIY-er.
Likely, the muffler shop will do it for similar money and much faster.

Back in the early days of catalytic converters, there were some old guys who… somehow… believed that their gas mileage would improve if they could get the cat converter to fail. So, some of these oldsters would purposely put leaded gasoline into the tank, in order to kill the CC and “improve” their performance and gas mileage. Boy, did they learn a lesson the hard way…

Of course, like most people who don’t understand a particular concept, a lot of them claimed that a massive government conspiracy was to blame.

I replaced a cat once and the warnings that came with it would give anyone pause to tamper with it. No one would do it for you for fear of fines and being shut down. Doing it yourself would open yourself up to same. Then if you ever had it in a shop I do believe they are required to report the issue or be subject to the same. I don’t have enough money or energy to fight the feds on something like this.

He may want to know because his has gone bad and Saab probably wants $1k to install a new one. Aftermarket cats often give a check engine light as if you had no cat. Been there, done that. Thanks, Magnaflow. And cats do go bad apparently. Had to put one on wife’s 2013 highlander, per dealer. It wasn’t cheap.

If it was one of the vehicles I drive (both 2005’s), they would’ve gotten cut off and spark plug defoulers inserted in the 02 sensor bung to remove the downstream 02 sensor from directly in the exhaust path. Check engine light is gone, no performance loss (or gain), and I’ll gamble that the government isn’t going to climb under my 14 year old vehicles to inspect. Dammit if they do.

If a vehicle comes into my shop and I find that the cat(s) has been removed, I tell the owner never to bring the vehicle back to my shop for repair.

Not all mechanics out there are hacks.


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