So, you’re in the market for an Audi with the 4.2 TDI diesel engine, and you are trying to find out more about its engine problems? If that’s the case, you are in the right place because, in this article, we’ll dissect each of the problems in great detail.
Doing your own homework before you make a purchase of a car with a certain engine is the right thing to do, especially when you’re buying an older diesel. You just don’t want to end up in a money pit full of problems. And from our experience, there are a lot of problematic engines that can be really expensive to fix. So, what are we going to cover in this article?
First, we are going to cover the specs of this 4.2 engine and then we are going to learn more about the common Audi 4.2 V8 TDI engine problems, as well as which models have the 4.2 engine. So, let’s dive into the topic.
Basic Audi 4.2 V8 TDI Engine Specs
The 4.2 VW/Audi TDI engine was developed in the early 2000s, with the official adoption year being 2005. This engine is still widely used to this day.
This engine was based on the 4.0L V8 TDI and was included in Audi’s luxury limousines like the A8.
What is interesting about the 4.2 engine is that it is a very well-engineered piece of machinery. Just like with every other Audi engine. And this has some positives and some negatives.
The positives are that you get something well put together, just like an expensive Rolex watch. The negatives on the other hand are the expensive repairs that come with these complex engine designs.
Nevertheless, these are the specs of the engine.
- Configuration: V8
- Displacement: 4.2L
- Cylinder Bore: 83 mm
- Piston Stroke: 95.5 mm
- Block Material: Cast Iron
- Cylinder Head Material: Aluminum
- Head Design: DOHC with 4 valves per cylinder
- Compression Ratio: 16.4
- Firing Order: 1,5,4,8,6,3,7,2
- Turbocharger: Yes
- Fuel Injection: Common Rail
- Horsepower: 320 – 349 hp @ 3750 rpm
- Torque: 479 – 590 lb-ft @ 1,600 rpm
Common Audi 4.2 V8 TDI Engine Problems
Common Audi 4.2 V8 TDI engine problems include:
- Carbon Deposits In Intake Manifold
- Intake Manifold Flaps Fail
- Timing Chain Rattle
- Glow Plug Failures
- Fuel Injector Clogged Up Or Leaking
- Clogged EGR
- Clogged DPF
- Turbocharger Failures
We briefly introduced ourselves to the common problems with the 4.2 TDI engine. Now let’s move on and elaborate on each one of these problems in-depth. We feel obliged to further explain these issues to you and share when and how they appear. As well as how expensive it is to fix these issues on your Audi.
Carbon Deposits In Intake Manifold
The first and most common problem with this 4.2 TDI engine is the carbon deposits that are accumulating on the intake manifold.
This is a very common problem on most of these diesel engines. The EGR valve is redirecting gasses into the intake and this doesn’t do any good to the manifold.
These deposits tend to stick to the walls of the intake manifold and eventually reduce the flow of gasses to the engine.
On some of the engines that have high mileage you will highly likely have very obstructed intakes, and you will probably have to get a new or a used manifold. Something which can be very expensive to do.
Intake Manifold Flaps Fail
Another thing that can often fail on the intake manifold is the flaps that open and close. These flaps allow air to enter the engine. Since on these engines, you don’t have throttle bodies like you have in gas-powered engines.
Instead, you have these flaps that open and close. They also fail, can end up being stuck, and not function properly. The actuators for these flaps can also fail and cause issues.
Many owners simply remove them completely and drive like that. This will potentially make your car produce more power. But it will not do anything good to your fuel economy.
Since more air is injected into the intake manifold, it will result in more fuel injected. In other words, the fuel consumption will increase and the engine efficiency will drop. So, it is best to find a used intake manifold if you can’t find a new one, or possibly a rebuilt unit.
Timing Chain Rattle
Timing chain rattle is also common on these engines. This is caused by either a stretched timing chain or bad timing chain tensioner.
Timing chains have a lifespan, they do not last forever as many people think. They just buy these expensive cars and think that they will run the engine forever without any maintenance. And this is a completely wrong way of thinking.
You cannot run the engine when you start noticing symptoms like engine rattle. In this case, you will highly likely need a timing chain job and you will have to replace this component along with the tensioners.
This is a very expensive job because the engine has to be removed and this costs a lot of money in labor.
This is why, before you buy any of these cars with the 4.2 TDI, make sure that the timing chain does not rattle or produce weird noises. A short rattle noise is best heard on a cold engine startup, and it only lasts for 3–4 seconds. Be on the lookout for that!
If it does, better stay away if you are not prepared to pay for servicing this engine.
Glow Plug Failures
Glow plug failures were also noted on this engine. So, what are glow plugs? Are they spark plugs?
Well, sort of. Glow plugs create heat and help ignition at cold start in diesel engines.
Spark plugs on the other hand are only used in gas-powered engines and they create spark to ignite the fuel. There is a major difference.
What is interesting about these glow plugs is that they should be replaced every 150,000 km or so. And what many owners do is never replace them.
If you never replace them, they will eventually bond with the cylinder head and it will be a complete pain to remove them.
And failures of these glow plugs on high mileage engines are a common thing. They fail, and you get the glow plug light and the check engine light. The car will be hard to start and will idle poorly.
They are not cheap to replace, but you have to in order to deal with this problem on your 4.2 TDI permanently.
Fuel Injector Clogged Up Or Leaking
Fuel injector problems on these engines are very common. These engines are mostly higher mileage, and you will highly likely have one injector that is problematic.
The injectors can end up being clogged up, or they can leak fuel. What is bad though is that these are not ordinary injectors that you have in gas-powered engines.
These injectors will cost you an arm and a leg to get them refurbished. Newer ones are even more expensive.
EGR problems are also common on these engines. The EGR is the exhaust gas recirculation valve and this valve can often end up clogged with carbon.
Some people clean these EGR valves. But this doesn’t always help and the EGR can be faulty once again. So, buying a new one is the safer alternative.
DPF problems are also common on these engines. DPF is short for “diesel particulate filter”. This filter is mandatory on newer diesel cars.
What can happen is that if you drive too much in the city or short journeys in general, you will not give the DPF filter a chance to regenerate and clean off the soot. In this case, you will end up with an obstructed DPF.
Make sure you read our article on how to recognize a blocked DPF filter to learn more.
There are companies that clean these DPF filters. They are able to remove them and manually clean them. It is expensive, but it has to be done in order not to have engine running issues.
Turbocharger problems are the last major issues that this engine suffers from. The turbochargers are also expendable components that wear out.
Whenever the engine reaches 200,000 km, you will have to either refurbish them or replace them with new units. They are expensive and can cost a good penny both to refurbish and to replace.
Used ones we will only recommend if there is no play in the shaft. If there is, this turbo is due to be refurbished.
Which Models Have The Audi 4.2 V8 TDI Engine?
Models that have this engine include:
- Audi A8
- Audi Q7
- VW Touareg
- Porsche Cayenne
What Are The Common Problems With The 4.2 TDI Engine?
Common problems with this engine include issues with the intake manifold flaps, injector failures, turbo failures, glow plug failures, DPF and EGR ending clogged up, as well as timing chain rattle when the timing chain is worn out.
Make sure you read our guide on how to drive and maintain a diesel engine to avoid engine problems.
Is The 4.2 TDI Reliable?
Yes, this engine is very reliable, if you purchased it new. But nowadays these engines have more than 200,000 km at best. This means that the engine will develop some of the problems common to diesel engines which include EGR and DPF problems, turbo failures, glow plug failures, injector issues, and so on. So, maintenance can be very expensive on these high-mileage engines.
The block itself is pretty bulletproof and can be pushed for more than 500,000 km with good maintenance.