TDI No Power When Warm: Log File Analysis

AUDI A6 2.5 TDI, TT5, manufactured in December 1998.

new log file 03.07.07
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.

When the car reaches its 90-degree angle and I press the accelerator, it's really fun. It accelerates nicely and shifts smoothly, just as it should.
BUT, if I'm driving for about 30 minutes and that's 90% in traffic (water temperature 90°, oil temperature 100°), then it doesn't behave as it should. When the engine speed is around 2000 RPM, and I try to accelerate with about three-quarters throttle, absolutely nothing happens; it actually slows down. Only when I press the pedal all the way does it downshift, rev loudly, accelerate poorly, shift gears, and feel sluggish.

It doesn't show any errors in the VAG-Com system.

Perhaps one of you has an idea or a tip about where and how I should test something so that I can provide you with more information.

Thank you for reading and considering!

Perhaps you could tell us which language(s) it appears in?

Thank you for sacrificing yourself. What is LLT?

Hello.

Load air temperature .

Best regards, Charly.

@charlyfirpo
certainly.

@user
Please move your mouse cursor over the abbreviation.

The intercoolers (you have two of them) hardly cool down at all in traffic jams. If the intake air temperature gets too high, the engine will reduce power.

Check the long-term fuel trim (LLT) using VCDS.

The A6, in my opinion, has always only had one large engine. That's the small but significant difference compared to the Passat V6 TDI .

"Thank you very much; I'll look into the LLT."

mullemaus wrote:

I think the A6 has always only had one [engine type]. That's the small but significant difference compared to the Passat V6 TDI

.
Really?

Today on the highway.

In summary, the higher the gear, the higher the engine speed needs to be for it to respond.

"When I'm at 1500-2000 RPM, it accelerates in second gear, the same in third gear, but very poorly. If I'm below 2200 RPM in fifth gear, I can essentially move the accelerator pedal between nothing and almost full throttle without the car accelerating; it only starts to accelerate when I press the pedal all the way down, at which point it also shifts down."
The unpleasant thing is that the car shifts into a higher gear at around 2000 RPM when driving in city traffic, and then I have 1600 RPM. If I give it more gas, nothing happens. So, if I press the accelerator fully, the car kicks down, but I take my foot off the gas because I'm in city traffic. The car shifts back into the next higher gear, and I'm driving again at 1600 RPM.

On the highway, I have to rev the engine to over 4000 RPM in fourth gear before shifting into fifth.

I hope these lines tell you something .

This morning.

Outside temperature: 19°C. Distance to work: 24 km.
The car is running perfectly (just like it does every morning), I love my car, but if the engine gets too hot or it's hot outside, or whatever bothers it, then it doesn't work as it should. See my post from yesterday.

Perhaps this will help with the diagnosis.

I've now read and browsed for about an hour, and I'm wondering if it could be related to my turbocharger/variable geometry turbine.
Can I move the control rod with my fingers when the engine is not running?

EDIT:


My first log file from the third floor.
Everything went well on the way home; I waited for 1 hour and then he left with me.

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.

Please don't immediately criticize me if it's not perfect, but I'm just glad I managed to do it.

Hello user,

I'm not a professional, but the values from your throttle pedal sensor seem questionable.
"During full-load acceleration, the value should always be approximately 100%. Can you do that while stationary?"
(Engine off) test MWB 10 [Throttle]. Observe (should be 0 at idle and 100 at full throttle).
You might have found your mistake here.

Good luck!

Apple23

Apfel23 is right. Somehow, I'm not understanding the values. Either you didn't give it full power, or there's a problem there as well. Maybe someone will chime in about this.

In addition, your LLM is producing extremely poor results. Since I can't interpret your LD values, I don't know if the problem lies with the LD itself.

Could you please compare the target (LD-Soll) and actual (Ist) values? Are the values reasonably close to each other?

Okay, so let's check the logs again, this time with the "LD" (likely referring to a specific system or parameter) enabled and set to its maximum value ("Pedal am Anschlag!!!"). Everything else seems fine; just swap out Block C to test the LD (I think it's MWB11). While you're at it, quickly check your maximum LLT (likely another parameter). I think we already have a good idea of the problem, but we need to narrow it down further to either the LD control or the LMM (likely referring to mass airflow measurement).

With the "Vollgas" (full throttle) setting, the problem might be that it triggers a kickdown, which could explain the observed value. It's just a suspicion/explanation.
Today, I achieved a better result with the Lokfile using gears 3 and 4, with a MWB (Mean Weight Braking) of 3.8 and 11.

Please double-check it. As I said, it runs perfectly fine in the morning, which is great, but if the engine gets too hot, then things go downhill quickly.

Everything smells like exhaust fumes. The actual value should be around 850, but mine goes up to 900. And if that's the case, the diesel injection is reduced because the control unit thinks it would otherwise produce excessive smoke (the soot limit for me is 60). But that's not actually happening. That's why you're experiencing a lack of power.

So, you just need to get the replacement part from Volkswagen, which costs around 75 euros, and it will work again.


Best regards.

Rainer.

It sounds like it's not as bad as I thought; I was expecting something worse. I'll try replacing the mass airflow sensor.
Question: But why does it work perfectly fine in the morning? No, no, I still want to use the LMM version; I'm just curious.

Your log files are a bit difficult to read because you don't seem to be running at full throttle for long enough, but that doesn't matter. The fact is that even with the engine idling (or over-revving), you still have much too low air mass.

"Why is it temperature-dependent? Perhaps because the mass airflow sensor (MAF) should "correct" itself based on the intake air temperature, which it isn't doing in your case. Somehow, the MAF needs to take temperature into account to report the correct amount of air... The cooling effect on these sensors is less pronounced with warm air, but they still need to report the correct airflow."

I can't explain it any better, and I'm not even sure if I'm right. But honestly, I really suspect it's the mass airflow sensor (MAF). Buy one (preferably through a trade!), and try again. It's not that expensive. I think it's probably over €75, more like €100-€110 including VAT. But get an original part from Audi/VW, not some cheap junk from 321 or A..U!