2012 S4 Problem List

[WimpyS4]

I have a higher mileage B8 S4 and have been slowly building it up. Recently I ran into quite a few issues so I thought it might be helpful to post a bulk list so people don’t have to run through the forums for hours finding a solution. I’m currently stage 1 APR with a cold air intake and stock exhaust with test pipes and I have about 130k on the clock. If I missed or need to update something let me know.

Issue #1
Motor Mounts: No engine code
The stock motor mounts on these cars will eventually go out or leak because they are hydraulic from the factory. These will cause other VERY expensive issues if they are not fixed relatively soon (break the cat flange). I went to a couple local shops and they all quoted me about 3-4 hours for this issue generously . Simple and relatively cheap repair. Motor mounts will run you about $430 and you can either get billet or cushioned depending on your preference. I personally went through FCP Euro because they promise a lifetime guarantee so if they do go out, I at least have some hope.

Issue #2
Catalytic converters: P0420, various misfire codes.
This was the biggest headache personally. I went stage 1 APR August 2020. About 3 months later I start getting misfire codes that will not go away. I thought it might be spark plugs so I bought new NGK’s and gapped to .034 which was ~ recommended spec (down to personal preference everyone will have a different opinion). That did not work so I replaced fuel injectors with redcaps. More expensive but needed to be changed anyways. Found out after scouring the forums for what could be wrong that the catalytic converter was most likely blocked/melted (even stock S4’s can melt the catalytic converter with hard driving and high mileage). Did some ratchet work and stuck some wire up from the downpipe so I didn’t have to pull the whole cat out. It worked for the time being and let the melted cat breathe a little. After some time, the motor mounts let the engine shift too much and snapped the flange. Definitely recommend strengthening the weld if you get the chance. Replaced with test pipes, put some o2 spacers and no codes so far. 2021 EPA made it impossible to find a tuner other than 034 motorsport to get a test pipe tune unless you go APR ultracharger (may change in the future). I used JHM test pipes and had the shop inspect the weld because these can sometimes break as well. 16 hour repair later (blocked cat melted bolts to manifold) and she purrs.

Issue #3
Mechatronics unit: P0751, P0753 (Shift Solenoid code) Usually only affects B8 models as this seems to be fixed on B8.5 and up.
Car started shifting rough from 2nd – 1st and would occasionally get “TMPS & Gearbox Malfunction” which I would just shut the car off and turn it on and it would work normally. Had local stealer look at it quoted me $2k to replace mechatronics unit. This issue is relatively common on B8 transmissions. Some cases you can get DSG tune on it and a gearbox mount replacement ($50) and it may be fixed. Mine eventually threw P0753 and stopping and starting would not fix. This means the mechatronics unit went out so you can either drop it off at a stealer and hope you get a $2k mechatronics repair (was quoted around $5-6k by other stealers) or buy the mechatronics repair kit from ECS (which is a audi/vw genuine part) and install it yourself (many local Audi shops refused to install). Install takes about 3 hours and requires you to pop the bottom of the trans off. Link to DIY who did it (Mechatronics repair kit is done, with a little DIY......... (audizine.com)). Not terrible to DIY but hard if you don’t have a lift. I had a local shop referred by the stealer (Matrix Integrated, Oregon). They did the whole repair for around $1400. Certain transmissions depending on manufactured year uses plastic gaskets which break when you take them off so keep that in mind if you DIY.

Issue #4
Tire wear issues.
This is my first real performance car and had no idea about the amount of camber on these cars so bear with me if this is common knowledge. I had a pair of $400 Nokian winter tires that came with the car and I did around 20k with them in less than a year. Found out inner edge was wearing faster than the rest of the tire. Split the sidewall from the tread and had to replace. When you rotate your tires, have the shop flip the tire so the outside goes to the inside.

Issue #5
Control arms (specifically front)
If you notice creaking from your car when you turn, your control arms are most likely going out. Easy and cheap repair. These go out faster than normal cars so if you’re like me and this is one of your first Audis keep this in mind.

Edit:
Did a cross country drive at apr stg 2 dual pulley and had another random issue. @145k miles

Issue #6
Oil cooler gasket leak
I had a seeping leak for a while and never paid too much attention to it. After the trip I noticed that it was dripping oil from the pan and found that it sheared two of the bolts off the cooler. Replaced gasket and bolts and no more leaks.

Apologies for the longer post just want to make sure people know what they are getting into when they get a nice deal on a B8 S4.

[RosSauce]

Great info, thanks! I posted something similar as I just recently bought a high mileage B8 S4 and found some of these issues by digging through a lot of posts and spending hours researching so it's nice to have it all in one place. My car was dealer serviced over its life and still needs ~$5K worth of work. It's actually in the shop right now for about a week to get a bunch of oil/coolant leaks repaired, a low fuel pressure code looked at, carbon cleaning, and front control arms replaced. It's annoying since with these leak issues you might as well get everything done/replaced as preventative maintenance due to the somewhat labor intensive work involved.

Definitely check around for oil/coolant leaks, PCV issues, and history of thermostat and water pump replacement. The constant heating and subsequent cooling from the supercharger seems to wear the plastic and rubber parts a bit prematurely. My shop was actually working on a 3.0T A6 when I brought my car in with the same oil/coolant leaks with only 75K miles on the odometer. I also would advise buying a B8.5 or a B8 with a transmission replacement or history of mechatronics/transmission repair if going the DSG route.

[WimpyS4]

Great info, thanks! I posted something similar as I just recently bought a high mileage B8 S4 and found some of these issues by digging through a lot of posts and spending hours researching so it's nice to have it all in one place. My car was dealer serviced over its life and still needs ~$5K worth of work. It's actually in the shop right now for about a week to get a bunch of oil/coolant leaks repaired, a low fuel pressure code looked at, carbon cleaning, and front control arms replaced. It's annoying since with these leak issues you might as well get everything done/replaced as preventative maintenance due to the somewhat labor intensive work involved.

Definitely check around for oil/coolant leaks, PCV issues, and history of thermostat and water pump replacement. The constant heating and subsequent cooling from the supercharger seems to wear the plastic and rubber parts a bit prematurely. My shop was actually working on a 3.0T A6 when I brought my car in with the same oil/coolant leaks with only 75K miles on the odometer. I also would advise buying a B8.5 or a B8 with a transmission replacement or history of mechatronics/transmission repair if going the DSG route.

Haven't had any leaks so far that I've noticed but thanks for the heads up. I'm planning to do water meth to keep the supercharger a little cooler to prevent any major issues with the pcv valve & heating. Also supposed to keep carbon deposits at bay but waiting till I get that installed to see the effectiveness. One of the shops that worked on it most recently said the supercharger flaps are also another thing that can go out pretty frequently. At this point I'm just looking at leasing a B9 as a daily and keeping my B8 as more of a project car.

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[Gkit19986]

I was quoted 10 hrs for motor mounts, for all of them ,not 3-4 hours.

[WimpyS4]

I was quoted 10 hrs for motor mounts, for all of them ,not 3-4 hours.

Damn I went to two shops in the area they both quoted the same. The shop might be just going off audis suggested quote.

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[djn876]

I was quoted 10 hrs for motor mounts, for all of them ,not 3-4 hours.

All of them being the full list above or just both motor mounts? There are only two. My friend and I did mine last weekend and it took us 3 hours or so having never done it before. 10 hrs is just crazy.

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[WimpyS4]

All of them being the full lost above or just both motor mounts? There are only two. My friend and I did mine last weekend and it took us 3 hours or so having never done it before. 10 hrs is just crazy.

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Yeah both motor mounts. I had a shop do them when I put test Pipes in because they already had the motor dropped anyways so they didn't charge me but 10 hours seems ridiculous

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[djn876]

For the tire item above, Nokian snow tires are going to wear very fast if you are driving them above 40 deg outside as they are not meant for those temps at all. Also for the tire wear/camber comment, the car from the factory does not run excessive camber. If it is lowered, it will run more and if desired you can correct with adjustable control arms, but unless you are crazy low, even that amount of camber is not excessive even for the street. More likely the bad upper control arms were causing the outside wear on the tire by allowing it to be misaligned more.

[WimpyS4]

For the tire item above, Nokian snow tires are going to wear very fast if you are driving them above 40 deg outside as they are not meant for those temps at all. Also for the tire wear/camber comment, the car from the factory does not run excessive camber. If it is lowered, it will run more and if desired you can correct with adjustable control arms, but unless you are crazy low, even that amount of camber is not excessive even for the street. More likely the bad upper control arms were causing the outside wear on the tire by allowing it to be misaligned more.

The wear issues were on the back where the control arms were fine. I got this recommendation from my tuner so I was just passing it along

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[toastsauce]

I have a higher mileage B8 S4 and have been slowly building it up. Recently I ran into quite a few issues so I thought it might be helpful to post a bulk list so people don’t have to run through the forums for hours finding a solution. I’m currently stage 1 APR with a cold air intake and stock exhaust with test pipes and I have about 130k on the clock. If I missed or need to update something let me know.

Issue #1
Motor Mounts: No engine code
The stock motor mounts on these cars will eventually go out or leak because they are hydraulic from the factory. These will cause other VERY expensive issues if they are not fixed relatively soon (break the cat flange). I went to a couple local shops and they all quoted me about 3-4 hours for this issue generously . Simple and relatively cheap repair. Motor mounts will run you about $430 and you can either get billet or cushioned depending on your preference. I personally went through FCP Euro because they promise a lifetime guarantee so if they do go out, I at least have some hope.

Issue #2
Catalytic converters: P0420, various misfire codes.
This was the biggest headache personally. I went stage 1 APR August 2020. About 3 months later I start getting misfire codes that will not go away. I thought it might be spark plugs so I bought new NGK’s and gapped to .034 which was ~ recommended spec (down to personal preference everyone will have a different opinion). That did not work so I replaced fuel injectors with redcaps. More expensive but needed to be changed anyways. Found out after scouring the forums for what could be wrong that the catalytic converter was most likely blocked/melted (even stock S4’s can melt the catalytic converter with hard driving and high mileage). Did some ratchet work and stuck some wire up from the downpipe so I didn’t have to pull the whole cat out. It worked for the time being and let the melted cat breathe a little. After some time, the motor mounts let the engine shift too much and snapped the flange. Definitely recommend strengthening the weld if you get the chance. Replaced with test pipes, put some o2 spacers and no codes so far. 2021 EPA made it impossible to find a tuner other than 034 motorsport to get a test pipe tune unless you go APR ultracharger (may change in the future). I used JHM test pipes and had the shop inspect the weld because these can sometimes break as well. 16 hour repair later (blocked cat melted bolts to manifold) and she purrs.

Issue #3
Mechatronics unit: P0751, P0753 (Shift Solenoid code) Usually only affects B8 models as this seems to be fixed on B8.5 and up.
Car started shifting rough from 2nd – 1st and would occasionally get “TMPS & Gearbox Malfunction” which I would just shut the car off and turn it on and it would work normally. Had local stealer look at it quoted me $2k to replace mechatronics unit. This issue is relatively common on B8 transmissions. Some cases you can get DSG tune on it and a gearbox mount replacement ($50) and it may be fixed. Mine eventually threw P0753 and stopping and starting would not fix. This means the mechatronics unit went out so you can either drop it off at a stealer and hope you get a $2k mechatronics repair (was quoted around $5-6k by other stealers) or buy the mechatronics repair kit from ECS (which is a audi/vw genuine part) and install it yourself (many local Audi shops refused to install). Install takes about 3 hours and requires you to pop the bottom of the trans off. Link to DIY who did it (Mechatronics repair kit is done, with a little DIY......... (audizine.com)). Not terrible to DIY but hard if you don’t have a lift. I had a local shop referred by the stealer (Matrix Integrated, Oregon). They did the whole repair for around $1400. Certain transmissions depending on manufactured year uses plastic gaskets which break when you take them off so keep that in mind if you DIY.

Issue #4
Tire wear issues.
This is my first real performance car and had no idea about the amount of camber on these cars so bear with me if this is common knowledge. I had a pair of $400 Nokian winter tires that came with the car and I did around 20k with them in less than a year. Found out inner edge was wearing faster than the rest of the tire. Split the sidewall from the tread and had to replace. When you rotate your tires, have the shop flip the tire so the outside goes to the inside.

Issue #5
Control arms (specifically front)
If you notice creaking from your car when you turn, your control arms are most likely going out. Easy and cheap repair. These go out faster than normal cars so if you’re like me and this is one of your first Audis keep this in mind.

Apologies for the longer post just want to make sure people know what they are getting into when they get a nice deal on a B8 S4.

Cheap and easy to do control arms?

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[WimpyS4]

Cheap and easy to do control arms?

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Yeah I would recommend meyle hd from fcp euro because they warranty them and have a whole video about how to do them. Tops are relatively easy but I'm doing the lower control arms now and it's a pia. You need some specialized tools too like a strut spreader from Amazon and a ball joint separator. Use generous amounts of penetrating fluid and make sure to jack up the front evenly or the sway bar that connects the front lower forward arm won't line up. Here's the video https://youtu.be/1Yc-y3o_kR4.
Pm me if u have questions ab it.


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