Audi A4 Turbo Problems - Solutions for the Faulty Turbocharger

The Audi A4 is a line of compact luxury vehicles that has been in production by the German car manufacturer since 1994. Available in both sedan and station wagon, the sleek designed vehicles offer outstanding performance and everyday functionality ideal for any type of driving. Evolving through five generational changes, the A4 model continues to be one of Audi's flagship vehicles even now.

The Audi A4 was actually the very first vehicle from the Volkswagen Group that was powered by the so famous 1.8-liter 20-valve turbocharged engine. With almost 170hp and 28 mpg on the highway, the combination of power and efficiency simply blew away the competition in the mid-nineties.

Key features and my opinion about the 1.8T engine

• Production years: 1996-2008
• Average lifespan of 1.8T: 190,000-220,000 miles
• Fuel supply type: port injection
• Power range: 150-180 hp
• Fuel efficiency: average
• Engine block material: cast iron
• Engine reliability score: high
• The most common problems: turbochargers may malfunction when the exhaust system isn't good, crankcase ventilation system problems, the timing chain tensioner isn't that durable, sensors are pretty faulty.

Presently, the Audi A4 model series offers an exciting selection of engine choices from TFSI gasoline to TDI units with forced induction and direct injection for exceptional pulling power.  

These vehicles are equipped with turbochargers to boost the engine's performance, making it faster and more powerful while improving the overall fuel economy. However, being a part of and/or related to the engine's oil, fuel, air, and cooling system, numerous reasons can cause the turbo in your Audi A4 to malfunction or get damaged.

So, for all Audi A4 owners, below are some common causes, symptoms, and recommended solutions to help you with your Audi A4 turbo problems. 

Turbo Problems and Solutions for Faulty Turbocharger

With a turbocharger, your Audi A4's engine can produce much more power and better performance than other vehicles with similar-sized standard aspirated engines. As the turbo gets more air (fuel) into the combustion chamber, this forced induction dynamically enhances the engine efficiency and power.

Also, improved combustion allows for a much better engine torque output, cleaner emissions, and a reduction in pumping losses within the engine.  

Unfortunately, a faulty turbocharger can have an opposite effect and cause your Audi A4 to underperform. Whether equipped with the latest TFSI inline-four-cylinder engine or a turbo-diesel option, turbochargers in the A4 models can fail due to a variety of reasons.

Although many issues are often invisible to the untrained eye, there are a few things to keep a look out for if you suspect any turbo troubles with your Audi A4.

• Problems with the Integrated Wastegate

Problems with the integrated wastegate can have a major effect on the turbo's ability to function properly. The wastegate is a valve that is responsible for allowing some exhaust gasses to bypass the turbine of the turbocharger. The venting of the excess exhaust gas ensures that the engine doesn't suffer from any overpressure.

On your Audi A4, the wastegate is controlled by a vacuum actuator through a short linkage. Hence, allowing the valve to open at higher engine speeds, controlling the excessive boost pressure. It is crucial that the amount of excess exhaust gasses released is controlled and doesn't hamper the turbo's ability to produce sufficient fuel for the engine.

Keep in mind, that the wastegate is attached directly to the side of the turbocharger, which is considered to be one of the harshest environments under the hood of your Audi A4. The surrounding temperature in that area can reach hundreds of degrees when the engine is running at high speeds. Under such conditions, leakage or other malfunctions may occur and disrupt the calculated release of excess exhaust gas.  

The valve in the exhaust side of the turbine housing, within the linkage, and in the vacuum actuator are three main potential places where wastegate problems can occur. Problems related to any of these components can end up letting the exhaust gasses out prematurely. As a result, there will be a shortage of exhaust gasses and the turbo will not be able to produce enough boost to function properly.        

Unfortunately, if there is a problem with the wastegate, the solution may not be a quick fixer. Since the wastegate is integrated into the housing of the turbo in your Audi A4, problems related to the wastegate may result in having to replace the entire turbocharger assembly. Of course, changing the entire turbocharger is very expensive and is not needed for most other turbo issues.  

• Due to the Diesel Particulate Filter (DPF)

The 1.9 TDI and 2.0 TDI of the Audi A4 series are both Diesel Particulate Filter (DPF) models and are commonly known to suffer from turbocharger failures. It so happens to be that the main reason behind the turbo failure is due to their Diesel Particulate Filters (DPF). The DPF in your Audi A4 is located in the exhaust and is responsible for trapping soot or ash particles.       

However, the DPF ends up restricting the airflow of the exhaust gasses and by doing so increases the back-pressure. Over some time, the excessive long-term back-pressure will put too much strain on all related mechanical components of your vehicle. Since the turbocharger of your Audi A4 is directly connected to the DPF, it is usually the first unit to suffer the consequences.   

The DPF cleans itself when you drive at a constant speed in top gear on the freeway. However, even after a regeneration cycle, a small amount of ash residue survives and eventually adds up and blocks the DPF. So, depending on the situation, you may need to replace or remove the Diesel Particulate Filter for a permanent solution.  

• Turbine Shaft Bearing Wear

The turbine shaft bearing wear is a common problem leading to turbocharger failures in the Audi A4 models. The turbos consist of a turbine wheel and a compressor that is driven by the engine's exhaust gasses. The turbine wheel spins using the hot exhaust gasses coming from the engine.  

From the high heat, pressure, and extremely high RPM of the turbine, the seals and bearing continuously get put under utmost load. The turbine shaft bearings hold the turbine in place while it spins at a speed going up to top rpm. Also, these bearings maintain the seals that keep oil and coolant inside the center housing.  

If these bearings happen to fail or get loose, they will cause the turbine shaft to clatter and create friction once the engine speed increases. Furthermore, if the seals are not maintained, then oil and coolant will leak through the exhaust. In case of any leakage, you will notice smoke coming from the exhaust of your vehicle.

On-time maintenance and proper lubrication is the best way to prevent premature turbine shaft bearing wear. Lubrication helps these parts to survive the extraordinary heat and pressure while properly functioning. Lack of oil or lubrication causes these parts to fracture, crack or break due to excessive frictions and heat during high-speed movements.  

• Compressor Wheel

The compressor wheel is another place where there can be problems that can cause the turbo in your Audi A4 to malfunction. It is not that uncommon for small pieces of debris or other foreign objects such as stones or pieces of metal to get past the air filter. Once it gets into the intake, these objects can strike and cause damage to the edges of the compressor wheel fins or blades while the wheel is spinning.  

Consequently, the balance of the turbo rotating assembly can get thrown off and result in a loss of boost pressure. Most times, you will need to first remove the turbo inlet piping and examine the wheel visually to diagnose the damage to the compressor wheel properly. Inspecting the air filter from time to time and changing it if necessary will help avoid foreign objects from ending up in the wrong places.  

Symptoms of Turbo Failure

There are a variety of signals that can be associated with your turbo failure. However, just by simply monitoring your Audi A4's performance, you can identify some of the usual symptoms related to the most common turbo problems. These symptoms will assist you to pinpoint the root of the problems and solve the issues before they cause further damage.        

• Grayish Blue Smoke

If you happen to notice any grayish-blue smoke from your parking mirror, that normally is a sign of oil leaks into the exhaust system. Whether from a crack in the turbo housing or damaged internal seals, oil leaking into the exhaust will burn with a distinct grayish-blue smoke. It is common for the fumes to increase as you start accelerating, driving at a high speed, and boosting your turbo.  

• Loud Whining Noise

Since the turbocharger muffles the noise of air intake, it actually makes the engine on your Audi A4 quieter than the engines that are naturally aspirated. So, if you can hear any loud whining noises coming from your turbo, your Audi probably has a broken turbocharger. As the condition of the turbo gets worse, so will the level of the noise.  

• Loss of Power and Speed

The Audi A4 is equipped with turbochargers to make your vehicle faster and more powerful. The turbo increases the power and capabilities of your vehicle and any changes in the performance can easily be noticed. So, if your car is underperforming, not accelerating as usual, or struggling to maintain high speeds, you're most likely experiencing a turbo failure.    

• Engine Light On  

The check engine light can appear on your dashboard for several reasons in your Audi A4. However, it is very common for the engine light to come on due to turbo issues. Whether it's something as serious as turbo troubles or just simply due to a loose petrol cap, it is best to have it checked out by a professional mechanic and find the exact problem.  

Conclusion

Turbochargers in the Audi A4 models are placed to enhance the power and performance of the engine. They are unbelievably reliable and very rarely fail due to any fault of the actual device. However, there are a variety of underlying problems and related mechanisms that can cause the turbo in your Audi A4 to fail.  

Proper maintenance, regular oil changes, and letting the engine time warm up a bit before driving can make a world of difference. The oil is as important as the blood flowing through the human body and is needed to circulate. Allowing 1-2 minutes for the oil to warm up before pulling off gives it time to get hot.  

Hot oil is thinner and can flow properly while lubricating the turbo and other mechanical components much faster. Also, after a long drive, it is advised to wait a few minutes before turning off the engine to avoid a backspin. That is not good at all and can cause damage to the seals, bearings, and fins on the turbines.    

To keep your turbocharger and engine running properly, it is recommended to change the oil more frequent than it's recommended. Although you can drive with a faulty turbocharger, the longer you wait, the worse and more expensive the problem will become. So, if you notice any of the turbo-related symptoms, you must get your Audi A4 properly diagnosed and solve the issue at hand immediately.