Catalytic Converter Questions for the 03 SLE

[Jrs3800]

Recently my 03 has been popping Catalyst Below Threshold codes.. I thought it was possibly the O2's getting a little long in the tooth.. 112,000 miles roughly... But as I was driving the car today I had to get down on it and I heard the cat rattle around 4500 Rpms... I was able to replicate the rattle...

Either way its done.. I have been looking at the Direct Fit units Like Magnaflow 24204 Direct Fit Catalytic Converter ...

Any info or suggestions would be appreciated..

[J Wikoff]

I think the "direct fits" of any brand for Bonnies still require welding at one end. The cat is welded into the entire cat-back exhaust like 92-99, correct?

Magnaflow's 49 state direct fit cat for our van fixed that code. Added a little rumble too. Be aware of some extra sound that you'll end up with.

[Jrs3800]

I may have to go this route.. And I would take it to an exhaust shop...lol

A little more rumble is ok with me as well...

[CMNTMXR57]

On Bonnevilles (going from mammory), the OEM unit has a square flange on the front of the converter (it's lead pipe), that separates it from the header pipe. It will need to be cut on the backside before the resonator though and then whatever you chose will need to be slip fit on then welded.

Looking at the Magnaflow 24204, it has the square flange, and has a slip over end at the end of the converter. So it looks to be a direct replacement. Being a slip-fit setup, you don't need to weld if you don't have it readily available. Just clamp it. You of all people can do this one on your own.

[CMNTMXR57]

Summit's picture;
http://www.summitracing.com/parts/MPE-24204/

[J Wikoff]

That's what I'd get, then.

[Jrs3800]

Summit's picture;
http://www.summitracing.com/parts/MPE-24204/

If it fits exactly as it should( slip fit ) Then yes I could clamp it as I have the good 2.5" exhaust pipe clamps and I am pretty sure the pipe ahead of the resonator is 2.5" ?

This converter may have been having issues for a while.. It tossed a code a couple of years ago on a long highway trip and I didn't see it again for almost a year... Then it was 6 months, 3 months, 1 month, 1 week....LOL

I never bothered with it as the car never felt like it was held back in any manner.. Ran good from idle to the max shift.. I wonder if the bed has simply shifted out of place, I think the rattle says yes....lol

I may just do the replacement myself..

[CMNTMXR57]

*Typically* when catalyst substrate rattles like that, it's an indication that it got hot and melted and/or broke off. If it isn't clogging anything you won't typically get anything for awhile. Certainly no low performance like many have issues with clogged converters, and it may be awhile until you get a catalyst below threshold code (P0420 I believe), if there is enough left there to do it's job.

Just sounds like it's time came and went. >100k is also on it, so you got your moneys worth for the most part.

[Jrs3800]

I completely agree... Its done its time... I give it no fault for wearing out.. Gas mileage has slowly been dropping off, no bad but not what it used to be.. So this explains a lot..

But like you said Its done 112,000 miles so its seen a useful life.. No complaints at all.. I do hope it'll have a little more exhaust groan with a newer converter

[CMNTMXR57]

Remove the resonator too while you're at it...

[harofreak00]

The Magnaflow 24204 does NOT fit, it is not a direct fit, nor does it slide over the existing pipe. I've tried installing them on 2 cars and it required more work than if I had just put in a universal. The slip-fit end is the exact same size as the original pipe. Do not recommend.

[CMNTMXR57]

Interesting? Does it bolt up to the flange? If so, it's just the pipe coming out of the convereter that can be flared.

[olblueeyesbonne]

I would highly recommend a universal fit Magnaflow from eBay or http://www.jmfmufflers.com/
I would recommend a 94106 universal 2.5" cat.
It's what I had in my old 98 SSE and my first 99 SSEi and did very well.

http://www.ebay.com/sch/i.html?_sacat=0 ... ow&_sop=15

[harofreak00]

Interesting? Does it bolt up to the flange? If so, it's just the pipe coming out of the convereter that can be flared.

Yes it bolts up just fine. Yes it could be flared, but that requires a special tool or an exhaust shop to put it in, the whole point of getting the direct fit is to avoid that.

[nos4blood70]

Remove the resonator too while you're at it...

Meh, better to at least put a glass pack or something.

Don't you have HPT? Just delete the code and put a test pipe in.

[CMNTMXR57]

No. Me trying to do tuning is akin to me trying to cook in the kitchen. Just something that no good comes of it.

[nconti13]

Ik I don't have much experience when it comes to this sort of stuff, but wouldn't getting a ZZP downpipe/high flow cat combo be a good option here (albeit a bit more expensive)? And am I correct in assuming that a bad cat would contribute to a decrease in MPG?