Catalytic Converter?

**Lawenforcer** · 02-18-2012

Hello,
I have a couple questions for you guys if you dont mind. I have two nephews that have Grand Prixs as well as me. One has a 2000 Grand Prix GTX. The other is a 2001 Grand Prix GT. They both are needing to put a Catalytic Converter on each of the cars. I was wanting to help them find a good deal on the internet for them but I am not exactly familiar with them. I dont want to order the wrong one and then have to pay like a re stocking fee to send it back if need be. I was looking at a couple like a SL Catalytic Converter part # SL013112329 from Auto Parts Warehouse. Something that would be cheaper on their pocket books but work for each of their cars. I am not really sure what Diameter of Inlet/Outlet that I would need to get for them to fit there car. We don't want to have to do any welding cutting etc....Unless we have to. I have never changed on out so not sure what I am getting myself into on helping them. I am actually thinking might need to be changed also so might just spend a weekend changing all of them out. Anyway, if anyone has any suggestions or can tell me the diameter that I need to be looking for on these, I appreciate all the help. Sorry I am new to all this and this is kind of a long drawn out question. Thanks Rich

**Fivefingerdeathpunch** · 02-18-2012

Sorta off the topic, but what makes you think they need to be changed?

Are they plugged up?
Are they causing constant rear o2 sensor codes??
rotten egg smell out the tail pipe??

I say this because if it aint broke dont fix it, they never need to be changed unless something is indeed wrong with them.

**Lawenforcer** · 02-18-2012

On theirs, Bad rotten egg smell and really bad gas mileage all the sudden. They also say that it is really loud and coming from the CAT. I am not sure what else it might be. I will talk to them some more about it but from everyone they have talked to say they need changed. As far as mine, I am not so sure, I am not really sure if it needs changed. It is still getting good MPG's, notice exhaust is a little loud while accelerating etc...but could be something else. Mine also has a Spectre Cold Air Intake on it, just cause it was already on it when I bought the car and it is somewhat loud when you start it up and seems to go away as the car warms up. So I am going to look further on my car before I go changing the CAT. Just cause I just purchased the car a week ago and still trying to figure it all out. I am totally new to all this so I feel stupid, but trying to learn as much as I can. Anyway, they say they want there CATS changed so I am just looking to help them out. Thanks

**Fivefingerdeathpunch** · 02-18-2012

I completely understand the whole helping part.

But bad gas mileage can be the cause of just poor maintence too, maybe a tune up is in order from them aswell. Though the rotten egg smell is a tall tale sign of a bad cat.

As for you intake noise, thats completely normal, is the rushing air past the IAC valve and just motor noise that a regular muffled stock intake wont let you hear. And loud exhaust while gaining speed, I would look at maybe an exhaust leak at the resonator and maybe over time the mufflers start to rot out on the inside a little.

**Lawenforcer** · 02-19-2012

From what I have been looking at online. Would I need to get a 2.25in diameter inlet and outlet to direct fit on factory exhaust without having to modify at all?

**Fivefingerdeathpunch** · 02-19-2012

The cat converter is welded into the whole downpipe.

You would either have to buy a whole downpipe section with a cat in it or, buy a cat and have a exhaust shop cut the old one out and weld the new one up in the same place.

The downpipe that is rusty brown on top is the cat downpipe, it will look very similar to whats on your car. see how the cat is welded into the unit.

**Tuner-Extraordinaire** · 02-19-2012

If there's no emissions they could just remove the cat and order a shelf tune with codes removed.

Cats don't improve mpg.

**z3r0** · 02-19-2012

Don't be a ***** get.rid.of.that *****

Android Fire

**asite57** · 02-21-2012

why would you put a cat back on a car cut it off straight pipe it, if its too loud put a better resonator on or better mufflers itll be cheeper and better

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