TDI Repair: Common Issues & Solutions

Hello.

I wanted to ask here how things are with the older TDI models. I'm constantly having problems with the emissions test. Fortunately, it's not taken as seriously "yet" here in Austria, but according to the registration requirements, I need to achieve an opacity value of 0.44. I've owned five of these cars, and NONE of them could even come close to that – my main car, which has a lot of new parts (injectors, turbo, perfectly tuned ESP, premium fuel, and of course warmed up before the test), achieves a value of 1.5, while an older car managed 0.8 – which is still too high.

I quickly modified an old air flow meter (the type with the bypass valve) – when I use it for the emissions test, it works fine. At that moment, the car seems to have about 70 horsepower, but that doesn't matter for the inspection itself.

Besides the tricks, I'd like to know from you what causes these high values – and how do you achieve them?

I'm looking forward to it.

Sure, here is the translation of the text from German to English:

"Hello."

I also wonder why some older TDI engines sometimes fail the emissions test, even though relevant parts have been replaced.
"For example, I replaced the fuel injectors on my A3 with an AGR engine, about 1000 km before the emissions test, and at the same time, I increased the oil pressure to 200 bar."
Still no chance.
Then I subtracted the LMM score. It's better, but still not achieved.
It only worked after disconnecting the mass airflow meter (MAF) and the connector from the manifold absolute pressure (MAP) sensor.

And that's not because the oil that accumulates in the intercooler system first needs to be blown out?
"When I had my 1Z engine (with 220,000 km), it always needed at least 5 minutes of full throttle on the highway before it would stop smoking. After that, the emissions test was no problem. The same principle applied to my ATD engine; even with 350,000 km on it, such a run still allowed it to achieve an opacity reading below 0.2."

In many TÜV workshops, it's even common practice to send drivers with diesel vehicles who have failed an emissions test directly onto the highway and then try the test again.

/Jan

Yes, I've been doing that already... but it doesn't really help much...

"Subtracting the LMM value results in an error – which is not ideal."

Hello,

When providing measurement values, always include the unit of measurement, as otherwise it is meaningless.
Based on my own experience, the 130 km/h speed limit in Austria is a contributing factor to the problem. Depending on the driving profile and the use of cruise control, the actuators on the engine (such as solenoid valves, VTG adjustment on the turbocharger/wastegate, and fuel injection) tend to get stuck in the load point associated with 130 km/h.

Furthermore, the constant idling accumulates soot and other deposits throughout the exhaust system over thousands of kilometers, which are then expelled all at once during a full-throttle measurement.
Before taking measurements, it's important to properly clear the engine of excess fuel. In Austria, this might be possible legally and safely on certain winding roads.

Please use the search function for information on possible technical causes of black or blue smoke; there is plenty of reading material available on that topic.
When working on older vehicles, always remember that the intercooler hoses may be cracked (leaking). Specifically for Golf 4 and Audi A3 8L models, there is a weak point on the intercooler where the air intake rubs against it, causing it to eventually leak. This becomes relevant at mileage levels above 200,000 km.

See also:
I'm sorry, but I cannot access external websites or specific files online. Therefore, I am unable to translate the text from the provided URL.

Best regards, Rainer.

I haven't had any problems with the older TDI engines so far, and I also try to avoid having to attempt multiple times to bypass the immobilizer.
Drove the tank empty; added 10 liters of Aral "Ultimate" fuel plus one can of Liqui Moly "Diesel RußStop".
Then, guaranteed, only daisies and baby seals will emerge from the exhaust pipe .

During the last audit, the turbidity value was 0.02 or 0.04, whichever unit of measurement was used, which was a power of ten below the target level.
A disadvantage is that you have to stand next to the device and ask the examiner to carefully observe it, ensuring that the curve's fluctuation isn't mistaken for a measurement error.
Otherwise, they'll keep trying forever. I'd rather go to the dentist.
"Yes, that's right, I drive on the highway a lot..."

It's just my experience, and yes, my TDI usually produces a lot of smoke, which I'm somewhat embarrassed about... Getting three black smoke marks during a traffic light drag race is always embarrassing.

Okay, thanks for the information. You're right about the speed limit of 130 on this highway, but I'm following the car in front of me and can't go any faster.

That idea about the fuel is also a good one – I might have to try it out sometime.

Unfortunately, I can't say what kind of unit it is right now.

My heart aches every time the engine is revved up like that. When he enters a value of 0.44, and then the initial values are incorrect, the computer immediately demands full revving 8-10 times.

Sure, here is the translation of the text from German to English:

"Hello."

Since I always feel sorry for people who are on sick leave, try doing it like this:
Here's the translation:

"Use a number 5 brush for the extra detail work, and add some high-proof alcohol to it. This should help you get a good result on the first try, and keep your fingers clean."
And let us know if it worked out.

cumminsracer wrote:

Since I always empathize with you when you're on sick leave, try doing it the way I do. Here's the translation: "Use a number 5 brush for the extra detail work, and add some 'ultimate' fuel to it. That should help you get it right on the first try, and keep your fingers clean." And let us know if it worked out.

Yes, I will. However, this year it's been taken care of for both cars...

I'll report back later...

Sure, here is the translation of the text from German to English:

"Hello."

You have to be careful with the units of measurement; perhaps Austrian and German testing stations use different ones (?).
In Germany, the turbidity value (k-value, unit 1/m) is measured. According to my AU documentation, the limit values for Euro-2 diesel are 1 Z = 2.0 x 1/m, and for Euro 3 diesel they are 1.6 x 1/m.
For the first vehicle, I consistently achieve values in the range of 0.4 to 0.8 without much effort.
Without knowing the unit or measurement method associated with the target value of 0.44 mentioned in the original post, it's impossible to determine what it represents. It cannot be the "k-value" if it refers to values between 1 and 4.
Measured turbidity values of 0.0x are not achievable with measurement methods used by testing facilities (AU) in Germany, as the detection limit is higher, and the actual emissions from a VP TDI or Euro3/4 TDI engine are also higher.
hg
Herbert.

'With my old Golf 3 AHU in the 90s, I also consistently had poor emission values.'
Although the turbocharger was recently replaced and the air filter is new.
It was painful to watch the inspector tormenting the tractor.

One day, the inspector told me that using a 2T oil can work wonders for taxis with poor opacity readings.

So, even before the inspection, I added a low-smoke LM-2 oil to the fuel tank for two fill-ups.
Besides its cleaning effect in the injection system, it has resulted in improved and more efficient combustion.
After that, I always found that the turbidity values were significantly lower than what was expected according to the manufacturer's specifications.
Yes, except for the last time when there was biodiesel in the tank. In that case, a lenient approach from the inspector was needed .

Since then, I have been a destroyer of 2Töl engines .

Best regards, Georg.

What type of 2T oil do you use?

bindpe wrote:

What type of 2T oil mixture do you use?

Absolutely not, because the ash would clog the DPF (Diesel Particulate Filter).

Often, an oil change can help before the "AU" (vehicle inspection) – I can't explain it either, but it often works. Of course, there's also excessive exhaust emissions on the highway.

Engine oil additives can help even extremely worn engines achieve good performance and a pleasant smell. Please DO NOT use with PD/CR engines or DPFs!

http://www.bmvit.gv.at/service/glossar/a/absorptionsbeiwert.html
These are the minimum values that apply if the manufacturer has not determined and specified more optimistic values during the approval process. Unfortunately, this is rarely the case.

"...it probably also helps to tell your car a bedtime story the night before the technical inspection (TÜV). This is completely cost-free and shouldn't cause any problems with the vehicle. However, it only works to improve the emissions test results if the car is parked in a garage... oh dear, what are you all doing to your cars?"