# Catalytic Converter Rattle Noise



## M3 E46 (Jun 30, 2009)

I have had my 2000 Golf 2.0, 5spd for about two weeks and I love it. I drive it on a daily basis and recently I started hearing a rattling noise coming from the cat only at lower rpm. Yesterday I confirmed that by lifting the car and the noise is coming from the cat. 
There is no cel, but when I did the obd scan there is a pending code p0304, misfire, which can be related to bad cat as well. 
Wanted to know if anyone has experienced the same? The car drives fine its just annoying to hear the rattling. What would be the best thing to do, go oem new cat or a aftermarket one? Don't want it to trigger a cel. 
Thanks!


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## bearing01 (May 27, 2004)

*Re: Catalytic Converter Rattle Noise (M3 E46)*


_Quote, originally posted by *M3 E46* »_a pending code p0304, misfire, which can be related to bad cat as well. 


How can a bad cat create cylinder misfire?
The rattle, are you sure it's inside the cat? How about the heat shield?
On my car the resonator rattles. It's a smaller version of a muffler that is located mid-stream in the exhaust system. It doesn't hurt performance. It's only annoying sometimes when turning in a parking lot or engine rpm is low enough to make it rattle.


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## M3 E46 (Jun 30, 2009)

*Re: Catalytic Converter Rattle Noise (bearing01)*

Thanks. Pretty sure its inside the cat. What have you done to stop it in your case? 
News to me too, read it on another forum where someone mentioned that po304 under one of many things can mean misfire/bad cat. Sounds weird to me too, just wanted to confirm.


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## bearing01 (May 27, 2004)

*Re: Catalytic Converter Rattle Noise (M3 E46)*

I wouldn't worry about that code. If the check engine light is currently off then that problem has likely resolved itself.
I didn't do anything to resolve my resonator rattle noise.
If there is an obvious piece of metal contacting the exhaust system you can try to ply it back out of the way. As for the cat internals, you can try tapping the cat with a hammer or block of wood. If you hear it rattle inside then that may help you pinpoint the source. Not much you can do to fix an internal rattle but to remove and replace. Quite an expensive job to fix a noise if the cat is still working properly.


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## Jay-Bee (Sep 22, 2007)

*FV-QR*

If you are under 120K you should get the cat checked out by a dealership, there is an extended warranty for them and you might be able to get it replaced for free.


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## M3 E46 (Jun 30, 2009)

Thanks guys! Unfortunantely I am 135K. Also since I just got this car, I do all of the car maintenance of my cars myself, and have already changed the oil (5-30 mobil) and have used the sea foam to clean the engine (car runs smoother since), is there anything else I should do to my car as far as reg maintenance goes that you would recommend? I plan on changing the spark plugs next weekend, oem ngk good choice?
Thanks!


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## bearing01 (May 27, 2004)

*Re: (M3 E46)*

single most important thing is to make sure the timing belt and tensioned have not exceeded 60k miles wear. You can change it yourself by following the instructions on this board.
After that, maybe replace the O2 sensors if they haven't been changed yet.


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## M3 E46 (Jun 30, 2009)

Thanks again! 
All 3 have been replaced about 5-6 months ago. How reliable are these engines if taken well care of? Also is mobil 5w-30 a good choice or would you guys recommend something else?


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## vdubxcrew (Jul 25, 2004)

*Re: (M3 E46)*

That rattling sound is the honeycomb media inside your cat coming loose. It happend on my 2000 as well. eventually it was clogging and performance was pretty bad. you have a couple options. #1) get a stock replacement, but they are not worth the cost...way too expensive. #2) get a highflow replacement cat off ebay for around $50 shipped and take it to a muffler shop and have them cut out the old and weld in the new for $20 or so. #3) unhook your catback from the cat, get a long steel rod and punch all the media out of the cat, vaccuum out what's left and run it gutted. Don't know what emisions are like in your state, though. It may or may not pass.


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## viper5b (Oct 30, 2005)

*Re: (vdubxcrew)*

ive already had this happen once...my 97 2.0 jetta, the cat came apart inside so bad that the car would not start...gutted it and ran it, ran good but the cel stayed on but mpg was down...my newer 98 jetta 2.0 i found the cat already gutted, im only getting 26highway and the cat makes a weird noise inside due to the giant empty chamber it makes...get a high flow or stock replacement...your car needs some backpressure...just do it right now and you wont have to worry, plus you'll pass emmissions...if you do gut it, at least get the muffler shop to weld in a straight pipe through the empty cat so it dont sound bad, it wont be as bad on mpg(it will still drop it), and it will create a tiny bit more backpressure than just a gutted cat alone


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## TMTuned99.5Golf (Jan 27, 2004)

*Re: (M3 E46)*

If the engines are well taken care of, they'll last a long time. I saw someone with a new beetle I think it was on here that the odometer just hitting 300k!!
The replacement motor that I ripped out of my car and replaced with the original AEG (see my build thread for info) had somewhere in the neighborhood of 190k on it.
Watch for some potentials of oil consumption, certain build dates of the AEG's had it, others didn't but that's extremely hard to tell when exactly it happened. Mobil 1 5w30 should be fine. As you creep up to the higher milege, maybe 200k or so, maybe try some 10w-30. A bit thicker so it shouldn't burn off as bad and still seal up everything nicely. Now if you debate between synthetic and regular oil, that's all personal choice and research YOU need to find. I know mechanics who swear by synthetic and others that despise it, all personal choice and knowledge basis.
Oh and when you do your next timing best, make sure to get the water pump that has the metal impeller. I've had a plastic on go out on me only after 15k miles yet I have the original ORIGINAL one the motor came with still intact after 161k miles!
You'll be very happy with the reliability of the motor and good luck with it. Ever have problems, don't be afraid to ask around here. We're a friendly bunch. http://****************.com/smile/emthup.gif


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## M3 E46 (Jun 30, 2009)

Guys, thanks a lot for all the info! Very helpful. The cel came on (p0422) due to the bad cat, and I will go the route of buying a new cat, non oem. 
What would you guys recommend? Are all of the aftermarket cats going to take care of the cel even the high flow ones? I found some on e-bay for about $180 brand new (cat+downpipe, no welding).


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## notreal (Feb 12, 2009)

*Re: (M3 E46)*

Ya, I had the same problem in my 2001 Jetta. Cat went bad, unfortunately like you, I bought it used at 130k miles, so I was out of the extended warranty. I wound up buying the Eastern Catalytic 40288 direct fit. (Only fits on AEGs). I have about 3 mpg better since the new cat has been in. No more rattling, and overall runs smoother.
Please make sure you do not buy the Magnaflow 23710. Their website says AEG engines, but if you notice, it is only a 4-bolt flange. Our AEGs are 6 bolts so the Eastern Cat works. The shop I used found this mistake, because I wanted the Magnaflow first.
Anyway, good luck!


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## Work2Bbroke (Jul 22, 2013)

M3 E46 said:


> I have had my 2000 Golf 2.0, 5spd for about two weeks and I love it. I drive it on a daily basis and recently I started hearing a rattling noise coming from the cat only at lower rpm. Yesterday I confirmed that by lifting the car and the noise is coming from the cat.
> There is no cel, but when I did the obd scan there is a pending code p0304, misfire, which can be related to bad cat as well.
> Wanted to know if anyone has experienced the same? The car drives fine its just annoying to hear the rattling. What would be the best thing to do, go oem new cat or a aftermarket one? Don't want it to trigger a cel.
> Thanks!


 I have exactly the same issue, not sure it's even worth changing it out if it can be avoided. Yes it's annoying but until it presents an issue I'm not going to do anything with it. Runs fine, why start replacing things that may cause a bigger hassle? :banghead:


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