The 7 Most Common Audi B7 S4 Engine Problems
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Trey is an automotive enthusiast and has a huge passion for Volkswagen and Audi vehicles of all kinds. His enthusiasm started with the MK5 GTI, and he has massively expanded his knowledge over the years. When Trey is not delivering high-quality and in-depth content, we can usually find him working in his garage on his modified Genesis coupe. Trey created VW Tuning several years ago, and he is the primary visionary behind the content.
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The Audi B7 S4, also referred to as 8E or 8H was the fourth generation S4. The S4 is the high-performance variant of the A4. There weren’t too many differences from the B6 to the B7 aside from some mechanical and cosmetic changes such as the headlights, taillights, grilles, etc. There were also some technological upgrades on the interior such as Bluetooth, Bose sound system being standard, navigation system, and more. We prefer the updated modern look Audi delivered with the interior and exterior of the B7. The B7 was built on Volkswagen’s PL46 platform and was first introduced in 2005 and production ran through 2009.
Audi B7 S4 Engine
The B7 S4 featured the same engine as its predecessor, which is a naturally aspirated 4.2L V8 (engine code: BBK) that put down 339hp and 302lb-ft of torque. Just like the B6, the engine had 40v, was a quad cam, with cast aluminum internals. Transmission options included a 6-speed manual and 6-speed Tiptronic automatic transmission. Although this engine won Ward’s 10 Best Engines two years running (2004 & 2005), many Audi owners have avoided it due to the timing chain issues it developed in the later years of the B6 and through B7.
Common Audi S4 B7 Engine Problems
- Timing chain failure
- Ignition coil pack failure
- VVT/Vanos solenoid failure
- Premature dual mass flywheel failure
- Mass airflow (MAF) sensor failure
- Valve cover gasket failure
- Faulty ignition switch
1. Timing Chain and Tensioner Failure – Audi B7 S4
The timing chain and the associated tensioners are regarded as the biggest problem with the S4 B7’s 4.2L V8’s and the reason why the engine has a bad rep. A timing chain connects the crankshaft and camshaft to control the opening and closing of the intake and exhaust valves. The tensioners are responsible for keeping the optimal tension of the timing chain to function properly. Without a functioning timing chain or tensioners, catastrophic engine damage will occur and the engine will die.
When it does fail, the valves and pistons collide which is a full engine rebuild and is not cheap. The timing chain provided by Audi is supposed to be a “lifetime chain”, but they don’t hold the tensioners to that standard which is the main reason for timing chain failure. If the tensioners on your 4.2 V8 haven’t gone out yet and you’re sitting at about 80,000 miles, we strongly consider replacing them to avoid a hefty repair bill.
Symptoms of Timing Chain or Tensioner Failure:
- “Death Rattle” – rattling sound on startup
- Engine dying
- Engine timing off
- Sluggish engine performance
- Engine not starting
- Stretched timing chain
Replacement Options:
If a B7 S4 timing chain fails due to tensioner failure, we highly advise replacing all of the associated components plus the timing chain (linked below). Given that the whole engine will have to be removed to perform this service, it is extremely difficult to DIY unless you have the proper equipment. Unfortunately, when this ticking time bomb does eventually happen, you’ll be looking to pony up anywhere from $5,000 – $8,000. However, if you were wanting to save some money, the kit below is probably well cheaper than what a dealer would charge.
Buy Here: B7 S4 Timing Chain Kit Replacement
DIY Difficulty: Difficult
2. Ignition Coil Pack Failure – Audi B7 S4
For spark plugs to “spark” in the combustion chamber and create combustion, they need electricity. Where does this electricity come from? Ignition coils or coil packs. They pull weaker voltage from the battery and transform it into stronger voltage needed by the spark plugs. Without functioning coils or plugs, there will be engine misfires or the engine could not even start.
Since the ignition coils are found in each of the 4.2 V8 cylinders, they are subject to high heat. This leads us to the main reason ignition coils or coil packs fail, normal wear and tear. The coils on this engine are likely to go out around 50,000 miles when it’s normal wear and tear. However, if the engine has been modified at all, this decreases the reliability and longevity of ignition coils and they can fail more frequently.
Symptoms of Ignition Coil Pack Failure:
- CEL or MIL illuminating
- Engine misfires with P0300 – P0308 fault codes
- Sluggish engine performance
- Rough idle
- Rough engine start
- Engine stalls
Replacement Options:
When an ignition coil goes bad, we advise replacing all of them at the same time. The reason we say this is because 1) it will cause fewer headaches in the future with all new ignition components and 2) it will avoid mixing new and old ignition parts. If you are needing to pinch some pennies, however, you could replace the faulty ignition coil and move on with your day, but expect more to go out after a short period. Replacing ignition coils and spark plugs is a pretty straightforward DIY if you have the proper tools and know where they are located. A mechanic would likely charge around $500.
Buy Here: B7 S4 Ignition Coil Pack Replacement
Buy Here: B7 S4 Spark Plug Replacement
Purchase Here: B7 S4 Upgraded Set of Ignition Coils and Spark Plugs
DIY Difficulty: Easy
3. VVT/Vanos Solenoid Failure
Since the B7 S4 engine uses variable valve timing (VVT or vanos) technology. The system changes the position of the camshaft, which allows the valve timing of the intake and exhaust valves to be more precise. The VVT system uses a solenoid that controls the camshaft timing. What ends up happening is the solenoid can get clogged or gunked up since it is actuated via oil pressure.
When a solenoid gets clogged, it will typically fail and cause engine performance and engine timing issues. It is typical for solenoids to fail or go bad every 70,000 – 80,000 miles, so if you are coming up to that point keep it on your radar. You will more than likely go through at least 2 sets of these through the S4 B7’s lifecycle.
Symptoms of VVT/Vanos Solenoid Failure:
- Rough idle
- Engine misfires
- Loss of low range power
- Decreased fuel efficiency
- Limp mode while accelerating
- Cold start problems
Replacement Options:
When a VVT solenoid fails, there are two options to choose from: clean them or replace them. Our suggestion would be to replace them because we can guarantee that you will not be able to get old solenoids near as clean as brand new solenoids. When you are just cleaning them, it’s more of a band-aid solution which could lead to decreased driveability down the road. Replacing a solenoid is not the hardest DIY if you know the location of said solenoids. A mechanic will charge around $200 to complete the service.
Buy Here: B7 S4 VVT Solenoid Replacement
DIY Difficulty: Difficult
4. Premature Dual Mass Flywheel (DMF) Failure
DMF failure is going to be more common in the manual version of the Audi S4 B7. The dual mass flywheel, or DMF, is found at the end of the crankshaft and it ensures a smooth experience when the vehicle is started, while the vehicle is idle, or when the engine is shifting gears. Without a functioning DMF or a rattling DMF, the driving experience will be less enjoyable.
When you start to hear the DMF rattle, because of a spring in the DMF failing, you will know it’s close to going out. It’s important to replace it ASAP when you hear it rattle because your driving experience will be dampened quickly. A DMF shouldn’t fail in a vehicle’s lifecycle, but with engine modifications or poor maintenance, they can fail more often.
Symptoms of Dual Mass Flywheel Failure:
- Excessive vibration on engine shutdown
- Rattle or banging noise from the bellhousing
- Clutch slipping
- Rough shifting
- Hard clutch
Replacement Options:
Whenever any of the above symptoms are being experienced, it is crucial to check the current DMF because if ignored it could cause major damage. There really is no way to repair a damaged DMF, so you will have to replace it and we advise going with an aftermarket unit, like the one linked below. Replacing this component is not an easy DIY, but there are videos and guides out there if you decide to tackle it and save the $600 – $800 a shop would probably charge for the service.
Buy Here: B7 S4 Dual Mass Flywheel Replacement
DIY Difficulty: Difficult
5. Mass Airflow (MAF) Sensor Failure
Many Audi and Volkswagen engines are susceptible to MAF sensor failure, and the 4.2L V8 is no exception. A Mass Airflow (MAF) sensor, as it sounds, measures the airflow that enters the engine. It is an important component in the engine’s fuel injection system and typically is located on the air filter and manifold. If it happens to clog or become faulty, the AFR’s will be thrown off which will lead to miscalculations of fuel.
The main reasons they fail are due to clogging, normal wear and tear from the engine’s heat or a collapsed air filter. The likelihood that one of these fails during the B7 S4’s lifecycle is high.
Symptoms of MAF Sensor Failure:
- CEL or MIL illuminating
- P0100 – P0104 fault codes
- Lean or rich AFR conditions
- Engine stalls
- Sluggish acceleration
- Difficulty starting the engine or not starting at all
Replacement Options:
When a MAF sensor fails, the only option is to change it out with a brand new sensor. This DIY, unlike many of the rest in this guide, is actually pretty straightforward and shouldn’t take longer than 30 minutes if you know where the MAF is located (which we’ve pictured above for reference). A local mechanic would likely charge around $300 to replace the MAF sensor on a B7 S4.
Buy Here: B7 S4 MAF Sensor Replacement
DIY Difficulty: Easy
6. Valve Cover Gasket Failure
A valve cover gasket failing and leaking oil on the engine is bound to happen in many Audi engines today. A valve cover gasket is a gasket between the valve cover and the engine. Its purpose is to seal engine oil inside the engine. The B7 S4 happens to have two gaskets: one on the left side and one on the right side.
These typically fail due to a lack of engine maintenance or engine heat which breaks down the gaskets over time. If the vehicle is maintained properly (regular oil changes, proper oil, high-quality fuel, etc.) then the valve cover gaskets should not fail in this vehicle’s lifecycle.
Symptoms of Valve Cover Gasket Failure:
- CEL or MIL illuminating
- Valve cover is visibly covered in oil
- Oil deposits on the engine
- Oil burning smell coming from the engine
- Engine misfires
- Low oil pressure light illuminating (More often than normal)
Replacement Options:
When you notice the valve cover gasket start to leak, the best bet is to just replace the right and left sides. Since the valve cover gasket is in between the engine and valve cover, you can imagine this is not the easiest DIY. However, there are videos and guides out there if you feel comfortable tackling this one on your own. It’ll save you about $250 in labor from a mechanic.
Buy Here: B7 S4 Valve Cover Gasket Kit Replacement
DIY Difficulty: Difficult
7. Faulty Ignition Switch
Although not necessarily in the engine itself, the ignition switch is a crucial component to start the engine. Unfortunately, these are common to fail in S4 B7’s due to being faulty out of the factory. An ignition switch, often referred to as a starter switch or just a start switch, not only starts the vehicle, but it also provides power to electronic accessories, the ignition, and the engine. So if it does happen to fail, the vehicle will more than likely not start.
The main reason the ignition switch fails is mainly due to them having a defect from the factory. Usually, an ignition switch should never have to be replaced.
Symptoms of a Faulty Ignition Switch:
- Car not starting at all
- Car key not turning
- Lights flickering on the dash
- Engine stalls
- No noise coming from the starter
Replacement Options:
If an ignition switch fails, it will have to be replaced. There isn’t a temporary fix for it that we know of. Since the replacement switch is relatively inexpensive, a DIY project would save at least $150 in labor. Replacing the switch should only take about an hour tops. If you were to go to a mechanic for this service, they would likely charge $200, mainly due to labor costs.
Buy Here: B7 S4 Ignition Switch Replacement
DIY Difficulty: Easy
Audi B7 S4 Reliability
As we prefaced a little bit in the introduction to this post, many Audi consumers avoid this engine because of the timing chain issues. Some have even said, “driving one with over 100,000 miles feels like sitting on a $2,000-3,000 dollar time bomb.” Car Complaints ranks the 2005 B7 S4 as the worst S4 to own. Ownerships are relatively high for this vehicle because it is on the higher end of luxury sedans when it comes to Audi vehicles. With all of that said, we have seen some B7 S4’s last up to 300k miles. So if maintenance schedules are followed to a tee and the vehicle is taken great care of, it is possible to have a very reliable B7 S4. Here is a thread for B7 service that may be extremely helpful.
If you are in the market for a used B7 S4, we would advise looking for a newer model year (2008+) and making sure to obtain maintenance records. Best case scenario the timing chain and everything associated (tensioners, chain guides, etc) have been replaced already. If not, we would avoid it as a failing timing chain can be devastating to the engine and your wallet. Let us know your experience with your B7 S4 in the comments below! Also, if you want to read more Audi content, here is a write-up of “The 5 Best Mods for the B8/B8.5 S4.”
