Audi S4 B6 Ultimate Guide

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The Audi S4 B6 was first introduced in 2003 and was the S4’s third generation. Unfortunately, it wasn’t in production for very long, it ended in 2005 for a much more modern S4 B7. It was built on the Volkswagen Group’s B6, or PL46, platform. The B6 S4 featured three different body styles: a 2-door cabriolet (convertible), a 4-door sedan, and a 5-door Avant. This S4 came with a new 4.2L V8 engine, something that hasn’t been featured in an Audi before. This engine quickly become known as a gas guzzler and didn’t have a great reputation because of the timing chains.

The 4.2 V8 engine replaced the 2.7T V6 engine that was found in the B5 S4. It put down an impressive 339hp (253 kW) and 302 lb-ft (410 Nm) of torque. It offered two different transmissions: a 6-speed manual and a 6-speed automatic.

Audi S4 B6 Specs

In this section, we will be going over the interior and exterior specs for both the two-door cabriolet, four-door sedan, and five-door Avant.

The 6 Most Common Audi S4 B6 Engine Problems

1. Ignition coil or coil pack failure
2. Timing chain failure
3. Carbon buildup
4. VVT/Vanos solenoid failure
5. Intake manifold linkage arms
6. Broken AC condenser or compressor

1. Ignition Coil or Coil Pack Failure

Premature ignition coil pack or ignition coil failure is very common in many VW and Audi engines. An ignition coil turns the battery’s lower voltage into the higher voltage needed by the spark plug. Once the spark plug receives this high voltage from the ignition coil, it then creates a spark in the combustion chamber starting the engine combustion process. There is one ignition coil and one spark plug for each cylinder. Since the S4 B6 has 8 cylinders, there are 8 ignition coils and 8 spark plugs. One failing ignition coil will likely cause engine misfires, while multiple failing ignition coils may cause the engine not to start.

There are many reasons ignition coils and spark plugs can prematurely fail: normal wear and tear, defective out of the factory, or modified engines for more power. The latter likely won’t happen unless you plan on putting a supercharger on the 4.2L engine. But if you plan to go this route, we advise getting 1-step colder spark plugs. As a general rule of thumb, spark plugs should be changed every 40,000 miles. Usually, you don’t have to replace the ignition coils, but we would just to avoid any near-future engine misfires.

Symptoms of Ignition Coil or Coil Pack Failure:

• Malfunction Indicator Light (MIL) or Check Engine Light (CEL) illuminating
• Cylinder misfires with P0300 – P0308 fault codes present
• Poor idle
• Rough engine performance
• Reduced fuel economy
• Difficulty getting the engine to turn over

Ignition Coil Replacement Options:

When an ignition coil or coils go bad, the only thing to do is to replace them. Our advice would be to change out all of the ignition coils and spark plugs at the same time. Although it may be more expensive, it ensures that all of the ignition components are fresh. This isn’t the most challenging DIY if you happen to know where these components are located. To replace all of the ignition coils and spark plugs in the 4.2L V8, a mechanic will likely charge around $750.

Audi S4 B6 Ignition Coils
Audi S4 B6 Spark Plugs

DIY Difficulty: Easy

2. Timing Chain Failure

Unfortunately, timing chain failure is inevitable on the S4 B6s and is mainly why these engines get a bad reputation. On a B6 S4, there are 4 timing chains, multiple guide rails, and multiple tensioners. The timing chains connect the camshaft and crankshaft to control the opening/closing of the intake/exhaust valves. The guide rails guide the timing chain to stay in place and the tensioners keep the optimal tension of the timing chain.

The timing chain should be a lifetime part according to VW. Given the guide rails are made out of plastic and the tensioners tend to prematurely fail, this causes major issues with the timing chain. If a guide or tensioner happens to fail, the timing chain can stretch or skip which could cause catastrophic engine damage. We’ve heard of some B6 S4 owners with broken valves and pistons because of timing chain failure.

Symptoms of Timing Chain Failure:

• Engine misfires
• P1340, 17748 engine codes
• “Death Rattle” on startup
• Limp mode engaged

Timing Chain Replacement Options:

Most cars have the timing chain near the front of the engine block, this engine has the timing chains near the back of the engine. In other words, if an S4 B6 has any timing chain issue at all, it will be a costly repair. If a timing chain guide or tensioner happens to fail and you are lucky enough not to have damaged valves or pistons, it can be rebuilt. However, a mechanic will likely charge around $7,500 to service this issue.

Audi S4 B6 Timing Chain Kit

DIY Difficulty: Difficult

3. Carbon buildup

Carbon buildup isn’t just a B6 S4 problem. It’s a common problem in many modern engines with direct injection engines. Direct injection is a term that means fuel is pumped directly into the engine’s cylinders via fuel injectors. This process can cause the valves and ports to be caked with soot or carbon over time. When buildup occurs, engine performance is dampened dramatically, depending on how much buildup there is. Imagine it like a stuffy nose for a clear nose. The difference in breathing is night and day. That’s exactly like clogged ports versus cleared ports.

This also tends to happen with engines that regularly take short commutes because the engines don’t heat up to optimal levels, it can’t burn off excess soot. However, once the engine is at optimal temps, we do a couple of redlines every commute to clean the valves out little by little. We would advise manually inspecting the valves and ports every 30,000 miles and cleaning if need be. If it is too late, you may need to get them walnut blasted at 60,000 miles, or when needed.

Symptoms of Carbon buildup:

• Engine misfires
• Rough idle
• Black smoke emitting from the exhaust
• Sluggish engine performance
• Rough starts
• Decreased fuel economy

Ways to Prevent Carbon Buildup:

• Replace ignition coils, spark plugs, and injectors regularly
• Change your oil and filter regularly, if not more than normal
• Use high-quality fuel, preferably at or over 93 octane
• Drive on the highway at high rpm’s for 20-30 minutes every once in a while
• Manually inspect the valves or ports every 30,000 miles and clean if needed
• Get the valves or ports professionally walnut blasted every 60,000 miles

4. VVT/Vanos Solenoid Failure

The 4.2L V8 engine uses Variable Valve Timing, often referred to as VVT or Vanos. This system variably alters the position of the camshaft, which allows for more precise exhaust and intake valve timing. This system uses a VVT solenoid which is activated by oil pressure to regulate the timing of the camshaft. These vanos solenoids tend to get clogged causing them to fail and lead to engine performance and timing issues. Vanos solenoids typically go bad around 70k-80k miles.

Symptoms of VVT/Vanos Solenoid Failure:

• Rough idle
• Decreased engine performance in low-end power
• Frequent engine misfires
• Decreased fuel economy
• Cold start issues
• Limp mode engages during acceleration

VVT/Vanos Solenoid Replacement Options:

When vanos solenoids go bad, the only thing to do is replace them. Cleaning them ever so often is preventative maintenance that is heavily advised. The part is not expensive itself, but mechanics will likely charge around $300 to replace one mainly due to labor costs.

DIY Difficulty: Intermediate

5. Intake Manifold Linkage Arm Failure

The 4.2L V8 engine also has a variable intake manifold. A typical intake manifold distributes air through one passageway to the cylinders. However, a variable intake manifold has two passages, a long passage and a short passage. An actuator controls a flap that delivers air to either passage. Now, this flap is held on by two manifold linkage arms which are made out of plastic, surprise. In true VW fashion, these are not the most durable and tend to snap very easily. When these “arms” fail, the actuator can’t function properly and redirect air into both passages. Therefore, engine performance is very hit or miss and you will be able to tell, as there should be a CEL or MIL light illuminating.

Symptoms of Intake Manifold Linkage Arm Failure:

• Engine misfires
• P2004 or P2005 fault code present
• Sluggish performance
• Engine hesitation while accelerating
• Decreased fuel economy

Intake Manifold Linkage Arms Replacement Options:

There are two options when the linkage arms fail: replace them with OEM parts or replace them with aftermarket parts. We highly advise going with aftermarket metal linkage arms. The dealership may try to get you to replace the full linkage arm kit, linkage arms and actuators, which in most cases the linkage arms are the only things that need to be replaced. With parts being about $100, a mechanic will likely charge around $400 in labor.

DIY Difficulty: Difficult

6. Broken AC Condenser or Compressor

This is actually one of the first AC condenser or compressor failures we’ve heard since writing about so many Audi and VW vehicles. So this is rather specific to the S4 B6. An AC condenser allows heat to be transferred from the refrigerant and transforms the high-pressure gas coming from the compressor into a high-pressure liquid. A compressor provides the circulation of refrigerant through the Ac system. So in essence, the AC compressor is the heart of the AC system.

Symptoms of Broken AC Condenser:

• AC blowing luke warm air
• Strange burning smell coming from the vents
• Engine overheating while idle
• Coolant leaking under the vehicle
• ECON indicator permanently on the dashboard
• Malfunction Indicator Light (MIL) or Check Engine Light (CEL) illuminating

AC Condenser or Compressor Replacement Options:

When the AC condenser or compressor happens to fail, there’s only one thing to do and that is to replace them. These are very difficult DIYs given the placement of the AC compressor. So unless you have a shop or professional experience, we would advise having a shop replace it for you. A mechanic or dealer can charge $750 or more to replace the AC compressor alone, mainly due to the amount of labor needed.

DIY Difficulty: Difficult

Audi S4 B6 Mods

Now that we’ve covered the common problems, let’s jump into the fun part. To be honest, the 4.2 V8 is already pretty tuned out of the factory, so it is quite difficult to get more power without spending a lot of money. But, the mods listed below, will make your Audi S4 B6 more fun. With the following mods, you may be lucky to add an extra 20-30 hp on top of the already impressive 339hp.

1. ECU Tune
2. Down Pipe
3. Catback Exhaust System
4. Sway Bars
5. Coilovers

Now if you’re looking for more than that and aren’t afraid to pony up some cash, go with a supercharger. There are many brands out there that make a supercharger kit, such as JHM or MTM, and it has B6 S4s running sub 12 quarters at 116 mph.

Audi S4 B6 Reliability

Is the Audi S4 B6 reliable? Unfortunately, the B6 S4 is regarded as not reliable because of the timing chain issues. However, if you are proactive with maintenance, they can be pretty reliable. It is important when driving that you let the engine warm up to optimal levels before doing pulls. We would advise if you are looking to get into a used S4 B6, make sure you have an indie mechanic, that knows this engine, and that you can trust. In the case that something does go wrong, the S4 B6 engine has extremely expensive repair costs. Some Audi dealerships have even said not to purchase a B6 S4 with over 60,000 miles that haven’t had an engine timing service of any kind.

If you are interested in more S4 content, here is an article on The 7 Most Common B7 S4 Engine Problems.