Engine Power Loss & Glow Plug Light On?

Hello!

My A3 is having problems again. The symptoms are quite clear and also occur regularly. I'll try to describe the current situation:

No problems or reduced performance on short trips, and normal performance as long as the engine is not at operating temperature.
When the engine is warm (water and oil temperatures are up), the power output noticeably decreases.
Sometimes, there's almost no power output up to around 2900 RPM, but then it suddenly reaches the usual performance level.
If there are any problems, the car sounds much duller and louder when idling (due to exhaust noises).
The preheating check light sometimes flashes shortly after there was no power: --> P0299 indicates that the boost pressure regulation limit has been exceeded.

Vehicle details:

8PA 3/2007 2.0 TDI quattro 125kw.
Engine replacement at 200,000 km, and currently at approximately 220,000 km.
LMM (Ladedruckmessung) replaced approximately 40,000 km ago.
K&N air filter installed.
To the best of my knowledge, this is the first particle filter, and it has at least 100,000 km on it.
The cable from the control unit to the boost pressure sensor was replaced.

I hope you can give me some guidance. Are there any recommendations for logging trips (which specific types of equipment)?
My initial thought is that it might be related to the particulate filter or the mass airflow sensor (MAF sensor). When I installed the K&N filter, I wasn't aware that it's not ideal for the MAF sensor.

I can provide the complete diagnostic report upon request, possibly in the evening.

Thank you very much!

Hello,

Quote:

I can provide a complete diagnostic report if needed, later this evening.

Please perform an auto-scan. While you're at it, please also run a data log for the turbocharger pressure control and air mass measurement systems, using measurement blocks 1, 3, and 11.

Please pay attention to the following:
I am unable to access external URLs, so I cannot translate the text from the provided link. Please provide the text directly, and I will be happy to translate it for you.

Best regards, Rainer.

Hello!

Here is the Autoscan log and the data logs from the test drive. After the warm-up phase, the described error occurred.

The DPF ash mass is 69g.

"Thank you!"

Quote:

The DPF ash mass is 69g

.
My question to you: How long do you think someone can continue driving with that, if the maximum value is 60g?

Next question: What do you think happens to the exhaust gas temperature if the turbocharger can't release its hot exhaust gases because the diesel particulate filter (DPF) is full?

Next question: What will likely happen to the turbocharger as a result of the previous question?

Best regards, Rainer.

Hello!

Since the car was last serviced at an authorized workshop in September 2015, and before that also regularly, I actually assumed that I would be informed when the particulate filter needs to be replaced.

I am fully aware of the consequences. I will schedule an appointment for the first week of February, as that's when I can also have the §57a inspection (technical inspection in Austria) carried out.

Is this the cause of the problems, or are there other factors to consider? (The DPF will be replaced anyway.)

Quote:

Since the car was last serviced at an authorized workshop in September 2015, and before that also regularly, I actually assumed that I would be informed when the particulate filter needs to be replaced.

Okay, that's something I would have definitely also expected in your case.
You can find the typical maximum values for ash content here: https://community.dieselschrauber.org/en/viewtopic.php?t=20333&highlight=maximale+aschemasse

So, the thing is, when the DPF is too full (with ash), the regeneration cycles become more frequent. This, along with higher exhaust temperatures caused by backpressure before the DPF, causes the turbocharger to experience even higher exhaust temperatures.

This is not good for its lifespan.

In your log, you can see that the boost pressure control is malfunctioning. This is almost always due to the turbocharger itself: the variable geometry turbine (VTG) has become stiff.
This can happen, among other things, due to overheating of the charger.

Of course, with your mileage, the jerky VTG could also be a simple sign of age, but excessively high exhaust temperatures due to a full DPF certainly won't make the situation any better.

During the installation of the replacement engine, it would have been possible to take care of the DPF with little additional effort...

I don't know how fit you are, but here are the things that need to be done now:
- Clean (or have cleaned) or replace the DPF: https://community.dieselschrauber.org/en/viewtopic.php?t=24243&highlight=dpf+reinigen
- Check the turbocharger. What's the problem and why? There's a lot of information available about the VTG, for example, https://community.dieselschrauber.org/en/viewtopic.php?t=2992&highlight=vtg.

Best regards, Rainer.

Hello!

The DPF will be replaced in 1.5 weeks by an authorized workshop. I can check the VTG, or they should also pay attention to it when replacing the filter.

"Of course, I wasn't informed about this during the engine replacement, but if I do a rough calculation, it seems like it should have been due for replacement there as well. Let's see if I can negotiate a discount on the labor if I mention this."

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

"LG" is an abbreviation for "Liebe Grüße," which means "Best regards" or "Best wishes" in English.

Tip: If it turns out that the charger is broken, it might be a good idea to combine the replacement with work on the DPF.