How common is blown cats on a stock S4?

[Misterjim]

I read through the "official blown cat" thread and was horrified to see that a number of people essentially suffered complete destruction of their cats with pieces literally blowing out of the tailpipe. I've never heard of such a thing on any other car. Sure cats can fail after 100k or more miles but some of these cars had only 60k or so miles. And to fail in such a way seems bizarre. Just how common is this? Does anyone know why this occurs? Are the cats that Audi uses defective? Out of warranty this could be an extremely expensive repair.

[Sick S4]

They tend to happen on cars that are heavily tuned (stage 2+) and its due to exhaust gas temperatures. I have yet to see a stock S4 with blown cats.


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[mcjim]

There are examples in the other thread of sock engines blowing the cats. I also am not sure it's the egt's other than maybe the cats are too close to the exhaust manifolds. Countless other super high performance motors don't have issues like this and Diesel engines which have way higher egts also don't blow out cats. I believe its design related


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[seandon_792]

There’s actually an entire thread of blown cats. Would link to it but on the phone right now [emoji53].


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[Venumous]

My drivers side went with 38k mi and was only stage 2 for 2k mi. They have certainly failed on factory tune. Mine was covered by 8 year 80k emissions. Would have been around $2k.

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[cspcrx]

I agree it’s a design issue. To early in the exhaust system. A bit further down and there would probably be no issues.

[Rodizzle]

They tend to happen on cars that are heavily tuned (stage 2+) and its due to exhaust gas temperatures. I have yet to see a stock S4 with blown cats.


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I had my left ( driver side ) cat blown at 46k ! STOCK no tune no mods !! Now I’m stage2+ at 61k I’m sure my cats are due to blown anytime soon


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[Sick S4]

I had my left ( driver side ) cat blown at 46k ! STOCK no tune no mods !! Now I’m stage2+ at 61k I’m sure my cats are due to blown anytime soon


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Did you buy the car used?


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[Rodizzle]

Yes , bought it with 29k Audi pre-certified


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[pedro sr.]

I read through the "official blown cat" thread and was horrified to see that a number of people essentially suffered complete destruction of their cats with pieces literally blowing out of the tailpipe. I've never heard of such a thing on any other car. Sure cats can fail after 100k or more miles but some of these cars had only 60k or so miles. And to fail in such a way seems bizarre. Just how common is this? Does anyone know why this occurs? Are the cats that Audi uses defective? Out of warranty this could be an extremely expensive repair.

There is a protective lambda-map in the Simos to keep the cat's from overheating. In high load/rpm situations for longer times EGT is a problem. The ecu is injecting more fuel above 950 degrees C to keep temperatures in check. If you have a tune and you see egt's of 950+ and a lambda value above 0.8 you can allmost certainly say this function has been deleted or altered to make more HP.

[spoolin80]

There is a protective lambda-map in the Simos to keep the cat's from overheating. In high load/rpm situations for longer times EGT is a problem. The ecu is injecting more fuel above 950 degrees C to keep temperatures in check. If you have a tune and you see egt's of 950+ and a lambda value above 0.8 you can allmost certainly say this function has been deleted or altered to make more HP.

so are there more conservative stage 2 tunes out (with a 180mm crank pulley) there that wont melt/fail the cats too prematurely? I want to go stage 2 just still worried about having the cats go at like 2k-10k :-/

[luciddream71]

Going from stage 2 to stage 2+ this Friday. No issues yet, but I can tell you I have a very short commute to work and don’t track the car; I mainly haul ass a round town in the morning when no one’s on the road at 530am. If mine go then it’s definitely not a heat issue as j hardly get to step on it for an extended period.


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[pedro sr.]

so are there more conservative stage 2 tunes out (with a 180mm crank pulley) there that wont melt/fail the cats too prematurely? I want to go stage 2 just still worried about having the cats go at like 2k-10k :-/

You can ask your tuner to set it up as high-torque and squeeze it above 6000rpm and keep cat-protective maps as they are i quess.

[spoolin80]

Going from stage 2 to stage 2+ this Friday. No issues yet, but I can tell you I have a very short commute to work and don’t track the car; I mainly haul ass a round town in the morning when no one’s on the road at 530am. If mine go then it’s definitely not a heat issue as j hardly get to step on it for an extended period.


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How long have you been stage 2? That sounds about how I drive mine...mostly weekend driving around town and just goosing it up here and there.

[4DOORFUN]

I starting to believe Audi bleeds off the boost at high rpms to protect the cats. It would be interesting to know if the RS4 uses different cats than the S4.

[pdqgp]

I starting to believe Audi bleeds off the boost at high rpms to protect the cats. It would be interesting to know if the RS4 uses different cats than the S4.

That would make sense.

[bhvrdr]

so are there more conservative stage 2 tunes out (with a 180mm crank pulley) there that wont melt/fail the cats too prematurely? I want to go stage 2 just still worried about having the cats go at like 2k-10k :-/

Most but not all of the tunes that retain the cat protection enrichment. APR runs a completely richer AFR throughout the full band under WOT. GIAC enriches like OEM does in the mid-upper band. Revo as well. As does Unitronic.

That being said just because you are using an enrichment strategy doesnt mean you will save the cats. If youre doing that to run more timing and boost like all of us are you still may kill the cats and ultimately, they may fail. I had 2 different 3.0T cars running either stage 2 or dual pulley and never had a cat issue but there are other people who have been through 3 or 4 of them.

Mike

[nicknice91303]

My drivers side went with 38k mi and was only stage 2 for 2k mi. They have certainly failed on factory tune. Mine was covered by 8 year 80k emissions. Would have been around $2k.

Sent from my SM-G950U using Audizine mobile app (http://r.tapatalk.com/byo?rid=87676)How was it covered with a tune added?

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[GandalfTheIbis]

so are there more conservative stage 2 tunes out (with a 180mm crank pulley) there that wont melt/fail the cats too prematurely? I want to go stage 2 just still worried about having the cats go at like 2k-10k :-/

The pulley ratio here is similar enough to the traditional supercharger pulley stage 2 method that I don't think there would be much of a difference. If you were talking about dual pulley then yeah going with a 180mm is somewhat conservative.

[pedro sr.]

Most but not all of the tunes that retain the cat protection enrichment. APR runs a completely richer AFR throughout the full band under WOT. GIAC enriches like OEM does in the mid-upper band. Revo as well. As does Unitronic.

That being said just because you are using an enrichment strategy doesnt mean you will save the cats. If youre doing that to run more timing and boost like all of us are you still may kill the cats and ultimately, they may fail. I had 2 different 3.0T cars running either stage 2 or dual pulley and never had a cat issue but there are other people who have been through 3 or 4 of them.

Mike

To my knowledge there are enrichment and timing pulls to save the cat's, but no boost-bleed over rfp. or throttle. In the end you will kill them if you use high hp settings over long time and experience misfires too much.

[GandalfTheIbis]

It's also a widespread enough problem that Audi does see a fair number of stock 3.0t cars with blown cats. My local dealership recognizes it as a problem with cars with this engine.

[Venumous]

How was it covered with a tune added?

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Flash to stock. Take car to dealer. Hope for the best.

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[quietcropduster]

How r u guys getting your CATs covered under the emissions warranty? Pretty sure my drivers side is starting to go.

Dealer is stating my CATs, are fine and it's an "exhaust leak" bullshit. Id imagine they have to take off the CATs to truly tell if 1 or both is going to be sure which requires the tranny to be out and they don't want to do that without the customer first offering to pay for the labor if it's not the issue.

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[Misterjim]

I had my left ( driver side ) cat blown at 46k ! STOCK no tune no mods !! Now I’m stage2+ at 61k I’m sure my cats are due to blown anytime soon


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Was the car stock for all of that initial 46k?

[Rodizzle]

Was the car stock for all of that initial 46k?
isfires.
Yes, my car was stock from the day I purchased it from Audi. Actually I take that back I believe at 43K I had installed a chipwerks Pro chip , then I started getting a lot of misfire/epc light here and there. I thought it was from the chip itself. No codes other then a misfire . I went into Audi ‘s dealership to get my tranny looked at and eventually got replace for a unrelated reason. When I got my car back I started to hear a noise that sounded like an exhaust leak. They couldn’t figure it out, Like I said there wasn’t no codes pointing to the cats . They did the timing change recall adjustment thinking it was that, they replaced the heat shield that covers and separates the engine bay from the cat thinking it was rattling without success. The noise was still there. Finally a Audi regional mechanic I believe came by and decided to drop a camera down my oz sensor . BAMM my driver side cat was completely melted .


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[quietcropduster]

isfires.
Yes, my car was stock from the day I purchased it from Audi. Actually I take that back I believe at 43K I had installed a chipwerks Pro chip , then I started getting a lot of misfire/epc light here and there. I thought it was from the chip itself. No codes other then a misfire . I went into Audi ‘s dealership to get my tranny looked at and eventually got replace for a unrelated reason. When I got my car back I started to hear a noise that sounded like an exhaust leak. They couldn’t figure it out, Like I said there wasn’t no codes pointing to the cats . They did the timing change recall adjustment thinking it was that, they replaced the heat shield that covers and separates the engine bay from the cat thinking it was rattling without success. The noise was still there. Finally a Audi regional mechanic I believe came by and decided to drop a camera down my oz sensor . BAMM my driver side cat was completely melted .


Sent from my iPhone using TapatalkSee i was told by the dealer they couldn't drop a sense down the o2 hold bec of the sharp angle and the camera not clearing it.

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[Rodizzle]

I would try another dealer to be honest with u , I think many of us have found out their cats been blown by the tech dropping a cam


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[LINDW4LL]

How r u guys getting your CATs covered under the emissions warranty? Pretty sure my drivers side is starting to go.

Dealer is stating my CATs, are fine and it's an "exhaust leak" bullshit. Id imagine they have to take off the CATs to truly tell if 1 or both is going to be sure which requires the tranny to be out and they don't want to do that without the customer first offering to pay for the labor if it's not the issue.
That seems stupid. Is the fault a "catalyst inefficiency" code?

What, if any, evidence is there of a leak, and is the supposed leak post-cat?

[quietcropduster]

I would try another dealer to be honest with u , I think many of us have found out their cats been blown by the tech dropping a cam


Sent from my iPhone using TapatalkMy car is going to the dealer again Friday. I got AoA involved this time. Car is out of manufacturer warranty but the 8/80 emissions warranty still applies.

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[quietcropduster]

That seems stupid. Is the fault a "catalyst inefficiency" code?

What, if any, evidence is there of a leak, and is the supposed leak post-cat?No CEL just the rattling noise. They blamed it on a leaking flex pipe. I had that replaced by independent shop, noise was still there, now I'm arguing with them to also get my $130 diag fee back.

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[Misterjim]

isfires.
Yes, my car was stock from the day I purchased it from Audi. Actually I take that back I believe at 43K I had installed a chipwerks Pro chip , then I started getting a lot of misfire/epc light here and there. I thought it was from the chip itself. No codes other then a misfire . I went into Audi ‘s dealership to get my tranny looked at and eventually got replace for a unrelated reason. When I got my car back I started to hear a noise that sounded like an exhaust leak. They couldn’t figure it out, Like I said there wasn’t no codes pointing to the cats . They did the timing change recall adjustment thinking it was that, they replaced the heat shield that covers and separates the engine bay from the cat thinking it was rattling without success. The noise was still there. Finally a Audi regional mechanic I believe came by and decided to drop a camera down my oz sensor . BAMM my driver side cat was completely melted .


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Wow. Sounds like the cats get too hot even when stock. I'm sure the situation is exacerbated with higher non-stock boost levels. Not good!

[nicknice91303]

Wow. Sounds like the cats get too hot even when stock. Not good!Hmm something I should ask about when looking to buy a 2014-2016?

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[Misterjim]

Hmm something I should ask about when looking to buy a 2014-2016?

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My same wonder. The problem is that it doesn't sound like you are going to be able to tell there is an issue unless it throws a code or rattles enough to be noticeable.

[Sick S4]

This car is probably one of the most reliable sports sedans I have owned. No matter what car you buy, especially a sports car, there will potential failure modes. The failure frequency appears to be very low for this failure as well as all of the other types of failures on this car (ie potential for your timing chain to make noise or slip, etc).
That being said.... if you want a sports sedan this is a no brainer of performance vs reliability.


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[nicknice91303]

This car is probably one of the most reliable sports sedans I have owned. No matter what car you buy, especially a sports car, there will potential failure modes. The failure frequency appears to be very low for this failure as well as all of the other types of failures on this car (ie potential for your timing chain to make noise or slip, etc).
That being said.... if you want a sports sedan this is a no brainer of performance vs reliability.


Sent from my iPhone using TapatalkI own a bmw E60 now and I'm looking to keep it but was shopping around for another "luxury sport" was between a bmw 535i msport, audi S4, jaguar XF. Looking to add mods such as intake, exhaust, tune, cosmetics, and coil over with a price range of 40-45 grand.. Not sure if I want CPO or just use.. all between 2014-2016

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[Sick S4]

I own a bmw E60 now and I'm looking to keep it but was shopping around for another "luxury sport" was between a bmw 535i msport, audi S4, jaguar XF. Looking to add mods such as intake, exhaust, tune, cosmetics, and coil over with a price range of 40-45 grand.. Not sure if I want CPO or just use.. all between 2014-2016

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You won’t be happy with the 535M (my opinion); not enough power in that big car. In my opinion, the S4 and Jaguar are the best choices here unless you are looking for the same room as the 5 series.

Between these 2, I go with Audi only because I have one and know what it’s capable of and I don’t know enough about the Jag (performance availability and potential, and it’s reliability concerns.

Do your homework on the cars but my best advice is to make sure you understand that you are going to read a lot more bad then good when you are searching for what issues exist in these platforms. Try to understand what the frequency of failure is (as OP is doing here).

You can probably tell but I believe the S4 is one hell of a car for the money you spend on it (especially when you wake it up with a tune and aftermarket performance parts).

Good luck with your car decision and hunt. It’s always a fun thing to do.



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[EIAlfonso]

I own a bmw E60 now and I'm looking to keep it but was shopping around for another "luxury sport" was between a bmw 535i msport, audi S4, jaguar XF. Looking to add mods such as intake, exhaust, tune, cosmetics, and coil over with a price range of 40-45 grand.. Not sure if I want CPO or just use.. all between 2014-2016

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Owned a 535M, beautiful car, power was more than adequate but nothing like the S4. The ride and feel was to comfortable and way to soft. Even in sport mode I remember the entire front the car lifting up like a '78 Olds

Answer to OP question, stock is probably 1 in 500. Don't use this forum as a gauge for stock cars, we're a bunch of crazy driving lunatics when compared to the general public
Tuned cars maybe 1 in 10, Ive been tuned stage 2 for 2 years and no cat issues so far, stage 2 DP for 6 months

[nicknice91303]

Owned a 535M, beautiful car, power was more than adequate but nothing like the S4. The ride and feel was to comfortable and way to soft. Even in sport mode I remember the entire front the car lifting up like a '78 Olds

Answer to OP question, stock is probably 1 in 500. Don't use this forum as a gauge for stock cars, we're a bunch of crazy driving lunatics when compared to the general public
Tuned cars maybe 1 in 10, Ive been tuned stage 2 for 2 years and no cat issues so far, stage 2 DP for 6 monthsThat s what I was looking at 2014-16 535 msport. But I have made up my mind and going to go with a S4 B8.5. And yes I want to tune it pullies; intake , exhaust and if I have to highflow cats. I would love to go with catless but here in CT finding someone to just turn there head in the emissions testing and passing it I'm sire is going to cause issues or throw up red flags. So I'm just gonna do what I want with it and leave the stock cats also do suspension coil overs but have not decided what brand to go with. I want it as close to stock as possible but springs will just mean replacing shocks after a short period of time..

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[Venumous]

How r u guys getting your CATs covered under the emissions warranty? Pretty sure my drivers side is starting to go.

Dealer is stating my CATs, are fine and it's an "exhaust leak" bullshit. Id imagine they have to take off the CATs to truly tell if 1 or both is going to be sure which requires the tranny to be out and they don't want to do that without the customer first offering to pay for the labor if it's not the issue.

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Has to be throwing codes. First they'll change your coils, then they'll do injector testing. If that doesn't pan out they'll maybe look at the cat through o2 bung.

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[quietcropduster]

Has to be throwing codes. First they'll change your coils, then they'll do injector testing. If that doesn't pan out they'll maybe look at the cat through o2 bung.

Sent from my SM-G950U using Audizine mobile app (http://r.tapatalk.com/byo?rid=87676)I'll look at the CAT thru my o2 bung myself, I have a camera. But good to know.

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[Venumous]

Yeah it's worth checking yourself. Mine was fd.

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[quietcropduster]

Yeah it's worth checking yourself. Mine was fd.

Sent from my SM-G950U using Audizine mobile app (http://r.tapatalk.com/byo?rid=87676)Fd?

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[GandalfTheIbis]

Fd?

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effed, fucked

[pdqgp]

Has to be throwing codes. First they'll change your coils, then they'll do injector testing. If that doesn't pan out they'll maybe look at the cat through o2 bung.

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All they have to do is swap coils around, check the plugs, put a scope in when plugs are out to see if coolant is leaking, then scope the O2 Sensor. If it's a cat the entire bank will likely misfire. if it's a plug or coil that one cycl. will be misfiring. give it a quick compression check, pressure check the cooling system, etc. Overall it's not that hard to diagnose so if they are giving you the run around they are newbs. which I doubt. They are just being difficult thanks to someone not wanting to pay for the labor of changing cats.

[quietcropduster]

All they have to do is swap coils around, check the plugs, put a scope in when plugs are out to see if coolant is leaking, then scope the O2 Sensor. If it's a cat the entire bank will likely misfire. if it's a plug or coil that one cycl. will be misfiring. give it a quick compression check, pressure check the cooling system, etc. Overall it's not that hard to diagnose so if they are giving you the run around they are newbs. which I doubt. They are just being difficult thanks to someone not wanting to pay for the labor of changing cats.Well duh lol, if the CAT (or both) r going out at 40k miles I have a rough time believing it's my fault.

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[quietcropduster]

My drivers side went with 38k mi and was only stage 2 for 2k mi. They have certainly failed on factory tune. Mine was covered by 8 year 80k emissions. Would have been around $2k.

Sent from my SM-G950U using Audizine mobile app (http://r.tapatalk.com/byo?rid=87676)What symptoms did u have? Mine is no CEL just a ticking type noise like a piece broke off and is rattling in the CAT. It's at 2500-3000rpm. Noise comes right thru the firewall by the hole for the steering stem.

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[quietcropduster]

There is a protective lambda-map in the Simos to keep the cat's from overheating. In high load/rpm situations for longer times EGT is a problem. The ecu is injecting more fuel above 950 degrees C to keep temperatures in check. If you have a tune and you see egt's of 950+ and a lambda value above 0.8 you can allmost certainly say this function has been deleted or altered to make more HP.I've monitored it on my Torq pro app. In 90oF heat doing a launch or pull the most I've ever seen for he CAT temp was like 1300-1400oF but then it came right back down.

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[Misterjim]

What symptoms did u have? Mine is no CEL just a ticking type noise like a piece broke off and is rattling in the CAT. It's at 2500-3000rpm. Noise comes right thru the firewall by the hole for the steering stem.

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How many miles on your car? Is the engine stock?

[quietcropduster]

How many miles on your car? Is the engine stock?45k and yes stock engine. I also don't beat on it, sides doing random highway pulls. Maybe seen 15-20 launches in its life.

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[Venumous]

What symptoms did u have? Mine is no CEL just a ticking type noise like a piece broke off and is rattling in the CAT. It's at 2500-3000rpm. Noise comes right thru the firewall by the hole for the steering stem.

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Misfired, cylinder shutdown, epc.

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