Kat Kaputt AFN.

Hello,

I have recently heard a distinct rattling noise at a specific RPM (approximately 1800 U/min). It has been getting worse, to the point where you can even hear it when the engine is off... I strongly suspect it's the cat, because when I tap on the cat with my fist (engine off), it sounds like there's a large screw or something else rattling around inside.

Am I right about my diagnosis?

Now my question(s): How complex is the replacement of the catalytic converter? Can I do it myself? (I have also already replaced various exhaust systems myself).
How much does something like that cost?

And now my most important question: Is a diesel particulate filter (DPF) worth it? I mean, is it even sensible to aim for a DPF replacement when replacing the catalytic converter, or is a filter completely independent? What could I save in the future by doing this (avoiding fines for particulate matter pollution, or also taxes)?

It is an Audi A4 Avant, manufactured in 9/96, AFN engine, with no modifications.

One more very important question: Can I still drive with the clattering cat for the next few days without risking further damage to any other part?

Thank you for your answers!

Best regards
mortl

Regarding soot filters, you should first work through the following technical article: /viewtopic.php?t=9140
As an alternative to a new cat, you could discreetly modify the KAT (catalytic converter) by cutting it open, removing the remaining parts of the monolith, and then welding it back together cleanly. This would allow you to pass the inspection (AU) even if the fuel injection system (and intake tract, turbo, air mass meter...) is in perfect condition, if you are using biodiesel or a mixture, and if the AGR (gas recirculation) system is defective. (This is because nitrogen oxides are not measured in that case.) Due to the lack of exhaust backpressure (and the defective® AGR system, which may have been damaged during optimization), fuel consumption could even be reduced and performance improved. This is only allowed off the public road, for motorsport purposes.

I would repair such an old car as cheaply as possible and wouldn't even consider adding a diesel particulate filter. However, your CAT (Catalytic Converter) has lasted a long time. Normally, they start to fail after 3 years or around 90,000 km. It's a common problem with older Audi A4 AFN models. Specifically, regarding the 1996 models.

Affordable cats are available here:

http://www.abgasprofi.com/

Greetings

Manuel

Hi,
Thank you for the answers, first of all.

Is there a quality difference between a 'Cat' from a company like abgasprofi.de and an original Audi/VW 'Cat'? If so, how significant is the difference?

Does 'Exchange-Kat' (from abgasprofi.de) mean that they want my old one, and I get a new one, or is it not a new one, but a reconditioned one? (Are there even reconditioned cats?).

Now, one more question, whose answer I am very dependent on:
How long can I drive the broken cat? Am I taking a risk (e.g., that other parts will be damaged - like the silencers, etc.)?
I mean: Do I have to leave the car immediately, or can I still comfortably commute to work (about 50km per day) for the next week?

As I said: if you tap on the cat's belly with your fist, you can clearly feel that something is moving inside, like a stone in a metal bucket (or something like that).

Best regards
mortl

I would like to fix this as quickly as possible.

My monolith had become twisted, and I could only drive at a maximum of 90 km/h.

'Exchange' usually means that he wants to have the old part!

Are they the same quality? I don't know, But for an original cat, you can use 4 imitation cats.

Greetings

Manuel

Now, one more question, whose answer I am very dependent on:
How long can I drive the broken cat? Am I taking a risk (e.g., that other parts will be damaged - like the silencers, etc.)?
I mean: Do I have to leave the car immediately, or can I still comfortably commute to work (about 50km per day) for the next week?


You run the risk that the cat slowly deteriorates and larger and larger pieces detach, which gradually clog your exhaust system --> The result can then be, as described above, that you no longer reach speeds over 90 km/h. I once had an Audi V6 ABC (petrol engine), where it worked well for a year, then it suddenly stopped. This then required a slightly larger intervention, completely dismantling the exhaust system from the catalytic converter and removing the pieces. Looking back, I wouldn't recommend it, as it won't lead to a lasting solution anyway.

I would like to purchase an inexpensive replacement cat, and if necessary, empty the cat temporarily. Should the transition phase last longer - of course, not for use under the road traffic regulations -, you should insert a blank pipe into the cat, otherwise it will sound very hollow.

Greetings
0588.778

Hello Mortl,

About 3 weeks ago (150,000 km), my cat {CAT_MODEL} {CAT_COLOR} {CAT_AGE} (makes a 'squealing' sound).

I bought a metal cat for 168 euros (including shipping) from a large auction house (with 'e' at the beginning and 'y' at the end, with 'ba' in between). This part looks very good!
Take a look at 'kat-mann' .

I temporarily removed (carved out) the defective monolith Warning:!!! Wear a respirator, extremely poisonous!!!, dispose of as hazardous waste ), in order to be able to drive at all.

Best regards, Kassen Oldewurtel