V6 TDI engine lacks power in warm weather

Hello,

I'm having a problem with the AFB V6 TDI engine in my A6 (manufactured in 1998, 200,000 km). The engine produces significantly less power when the outside temperature is above approximately 25°C. Below 25°C, everything is fine. The fuel consumption has increased by a good liter.

'The error log indicates 'boost pressure intermittently falling below the threshold.' The mass airflow sensor (MAF) has already been replaced, and the engine previously went into limp mode, but it's no longer doing so.' LMM was mentioned in the error memory, but it is no longer there.

Now the question is, what else needs to be replaced to ensure the engine runs well even in good weather. The difference in performance is significant. You can especially notice it when starting, but also in all speed ranges. You simply need to push the accelerator pedal a lot more, and the turbocharger kicks in at a very low 2000 RPM, which is quite weak.

Besides the 'boost pressure too low' error, there are no other entries in the error memory. I'm hoping it's a temperature sensor. Is there anything known about that? Or more likely, the turbo's magnetic valve control? The Turbo-VTG can be easily moved.

Furthermore, I believe the oil pressure drops after long highway drives. This is because you can hear the camshafts 'whining' when you quickly increase the engine speed in lower gears. It sounds like the first few meters when the engine is started for the first time that day.

I'm open to any suggestions, and thank you in advance!


Regards,

Sebs.

hi sebs,

I've been dealing with this problem for a long time, and I've already spent a fortune on repairs for the car, but unfortunately, without any results!
There are few parts that haven't already been replaced or inspected, but without any positive results!
When the climate changes, the problem of reduced performance in hot weather will become much worse! Three weeks ago, I almost couldn't get started at the Fernpass pass with a trailer (1.8 tons) because of this problem - I had to rev the engine to 3000 RPM and slowly release the clutch .

Sincerely,
(In the future - never again TDI)

Markus.

merlin wrote:

hi sebs, Sincerely, (In the future - never again TDI) Markus

More precisely, it's a V6 TDI.

Does your company completely close down during the holidays?
Have you ever considered disabling the LMM?

P.S. If everything has already been checked, then it should be working now.
It shouldn't be too difficult to pinpoint the cause of the error, since it seems to be happening consistently at high ambient temperatures, rather than sporadically.

Are the values from the temperature sensors all plausible?

Sebs wrote:

Hello, Furthermore, I believe the oil pressure drops after long highway drives. This is because you can hear the camshafts "whining" when you quickly increase the engine speed in lower gears. It sounds like the first few meters when the engine is started for the first time that day. I'm open to any suggestions, and thank you in advance! Regards, Sebs

Do you have an analog oil pressure gauge installed?
Since when can a knocking sound in an engine intensify? Usually, if there's a knocking sound, the connecting rod bearings and crankshaft bearings will start making a lot of noise first.
And in my place, I would also have all the temperature sensors checked first.

Hi Steffarn,


agr is completely closed - I installed an aluminum plate in between for testing purposes!


###
It shouldn't be too difficult to identify the cause of the problem, since your issue seems to be consistently occurring at high ambient temperatures, rather than being intermittent.

###

Yes, it seems it is difficult! For example, if the weather on the day the car is in the workshop is not warm.

Values seem to be all okay!
In addition, I'm experiencing a strong vibration under load, and it's running very roughly – almost clattering!

-Lmm is the 6th (I already had a diode installed, but it didn't make a difference).
-agr was already shut down.
- The turbocharger has been rebuilt twice and the VTG (Variable Turbine Geometry) linkage has been inspected.
- The valve timing was checked mechanically, which meant that the entire front section was disassembled.
- AGR valve replaced.
- The pressure regulating valve has been replaced.
- camshafts were inspected.
- The needle feed mechanism was possibly replaced with a different one.

In total, I visited 11 workshops in 3 different locations, costing approximately 2150 euros. The result? The same lousy quality as before.

and now someone should tell me, 'that must be findable' .

If anyone feels qualified, both technically and practically, to help me with this problem, I would be willing to invest another €1000 in the project/vehicle. Put money away for a rainy day!

Okay, here's the translation:

MBK: AKN / Mileage: 70,000 km / Year: 2000 / Model: Audi A4 Avant V6 TDI Quattro.

Best regards and thanks - still frustrated greetings.

markus

Yes, it's probably really not a piece of cake.
If it were my car, I would try swapping in a different control unit just to see if it makes a difference.
Unfortunately, it's not that simple because of the WFS (likely referring to a specific system or feature). You'll probably need to have it unlocked by an Audi dealership.

Otherwise, what is the boost pressure when the engine isn't producing power?


Perhaps a chip tuning modification might even help.

Tried chip tuning - forget about it!

'Alternative control unit - where can I get one?' Workshops don't just have those things lying around!
There is a charging current present, even though there is no power output! It's just that it's arriving a bit later.

Unfortunately, it's my car, and I don't have the money for a new one right now!

The fact is: if this problem isn't solved in a workshop soon, the car will end up in the junkyard somehow!
Then there will be a powerful gasoline engine again - although I doubt it will be from the VAG group!

I've received so many helpful tips in this forum, and I've tried everything I could, but unfortunately, nothing has worked.

Markus.

Hello,

I just realized that your list is missing the check for the boost pressure sensor (including the electrical connection). If the sensor is measuring too low, the fuel injection amount should actually be reduced --> resulting in a lack of power.

Okay, the turbocharger pressure sensor is another thing to check! Even though the values in VAGCOM seem okay (at full load), I'll remove the left front wheel and the splash guard next time I have the chance – that should give me access to the sensor.

You're welcome.

M.

merlin wrote:

Okay, the turbocharger pressure sensor would be another thing to check! Although the values in VAGCOM are okay (at full load), I'll remove the left front wheel and the splash guard next time I have the chance - I should then be able to access that thing.

If the LD sensor is really faulty, it will be difficult to diagnose the problem with VAGCOM, because the system is being regulated based on its feedback.

That would be quite helpful with an LDA .

Otherwise, one might potentially observe a revealing difference between cold and warm weather based on the low-density to total density ratio, even if the apparent pressure seems the same.
And of course, to the LMM values.

And possibly, a comparison of the ambient pressure and the boost pressure when the engine is stationary.

Have you ever logged the quantity limits (hoping that the V6 engines have the same limits as the 1.9 engines)?
If the fuel injection system is always injecting the same amount according to the readings, then the problem likely lies elsewhere, such as in the fuel system (which I am not familiar with on the V6 engine).

Good evening, everyone.

Okay, first, I'm glad to know I'm not the only one facing this problem. However, what I read next wasn't exactly encouraging. I have an appointment at the workshop next week, hopefully with good weather. The mechanics want to take a look at it and do a test drive with their diagnostic tool.

Let's see what happens, I'll keep you updated. The turbocharger pressure sensor seems quite plausible to me.

Thank you for your responses. Anyone who has any ideas or suggestions is welcome to share them.


Regards,

Sebs.

Hello Sebs,
Did the workshop find the problem with your car?

Regards,
Dieter.

Hello fellow V6 enthusiasts!

For a long time, I was also stuck on a strange appearance issue with my AKE V6 TDI, which had 170,000 km on the odometer. It's working again now.

Question: When the valve timing was checked, did YOU personally see the camshafts?

My Audi mechanic replaced the timing belt and said everything was okay. After that, I drove another 50,000 km with the problem. What was the issue? The camshafts were completely worn out.

I spent months searching for the problem myself and invested a lot of money, all because my mechanic didn't look closely enough. (I tried everything: ESP, mass airflow sensor, injectors, filters, sensors, control unit). I had completely relied on the fact that the valve timing was okay.

My tip: Take a closer look yourself! That's a real problem with these engines, especially with that much mileage.

Best, Knubbi.

I wasn't able to go to the workshop because the weather let me down. It simply wasn't warm enough, and this issue occurs approximately 2 weeks per year.

However, I doubt that the problem is related to the camshafts, as it seems to be directly related to the outside temperature. I'll get a new mass airflow sensor and other temperature sensors that measure the intake air temperature installed next year.

Okay, I'll keep looking. I just replaced the brake rotors and pads, and the hoses are still on. I'm still an apprentice, so I need to take things a little slower.

Uuuuugh.

Of course, this is also the right car for an apprentice. If the pump fails, you might have to take out a loan.

I would still suggest taking a look under the valve covers to see what's going on.

I would never have blamed the camshafts for my problem.

But, whatever. You need to know this.

Regards,

Knubbi.

@Knubbi,


If I may ask. What does it cost to have some fun?

And can we be sure that the material is better today? Because the number of camshafts hasn't changed.


Rainer.