TDI Performance Issues: Troubleshooting Guide

Hello...

'I've noticed since last week that my AJM TDI (115 hp, manufactured in 2002, 97,000 km) experiences a loss of power at approximately 2600 rpm.'

'So, when accelerating, especially in first and second gear, it almost feels like the car is being braked, as if the turbo briefly cuts out (the issue is sporadic but not rare). This whole process lasts for about a second. At high speeds, the car can just barely reach 180 km/h (I'm not sure if that was weather-related).'



During that period, I filled up with biodiesel twice, but I've been using regular diesel again recently.

What could be the error?

Thank you.
Ann.

A dying IMM?

Do you have any options for logging measurement values?

I don't know.
I'm not an expert in that area.

What is the actual cost of an LMM (lambda sensor) repair at a dealership?

Best regards, Ann.

In exchange, it's about 90 Tux if you assemble it yourself.

'But it doesn't necessarily have to be the LMM. That's why the LMM values during acceleration would be very interesting...'

...made on the highway.

Also Bergab macht er noch 200. BUT:
I tried the following while traveling at top speed:
Pulsating gas...
When I tried to accelerate again, the engine initially responded for about 1 second, then it seemed to lose power for another 1 second, and then it started working again.

I have the feeling that the car has generally become slower.

One IMPORTANT thing I noticed:
MFA: (Consumption display)

Under full load, I consistently got a fuel consumption of between 12.3 and 12.6 liters per 100 kilometers.
Jetzt schaffe ich es nicht mehr über 10,2 (bei 6. Full power mode.
I think that's related to the performance gap.

Could it therefore still just be the filter (due to RME operation)?


Thank you.
ANN

It could also be the diesel filter, a stuck VTG (variable turbo geometry), a leak in the intake manifold, or something else. What about soot buildup during the phase of power loss?

Therefore, as I mentioned, logs of specific sizes would be interesting. Without them, I think a correct tip would be a matter of chance.

No... I made sure of that.
Absolutely no soot at the rear.

Sure, here's the translation:

'One more question:'

Is the fuel consumption actually measured based on the amount of fuel that is injected?
(If the filter is closed, nothing can pass through it, logically.)

Regards,
Ann.

RaZoR wrote:

Is the fuel consumption actually measured in a way that accounts for what is injected?

No, the consumption is only calculated based on the control of the PDEs (and other parameters).
If the calculation model no longer accurately reflects reality (e.g., due to incorrect filter settings), the displayed consumption will also no longer match the actual consumption.

No, the consumption is only calculated based on the control of the PDEs (and other parameters).
If the calculation model no longer matches reality (due to incorrect filter settings, etc.), then the displayed consumption will also no longer reflect the actual consumption.


Therefore, a failing mass airflow sensor is quite likely, because it would measure decreasing amounts of air, and as a result of the smoke limitation, the fuel injection quantity would be adjusted downwards accordingly, which in turn would lead to lower values at the mass airflow sensor.

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

'Cu Gremlin'

What's the worst that could happen if I continue driving with this failing LMM (lambda sensor)?

Regards,
Ann.

not much, except that the air mass sensor (LMM) might eventually deliver a reading of 0 mg/stroke (I've personally experienced this with several units), and then you'll be driving around with a complete loss of power.

What's your problem now? Are you unsure about the diesel filter? Just replace it, and then you'll know.
On the other hand, you could also try using the famous diode as a replacement for the LMF (likely referring to a lambda sensor). If the power loss is better, then it's the LMF. If not, then you'll have to keep searching.

As I already mentioned, measurement logs would be the best. We could probably draw some conclusions relatively quickly from that data.

Is the mass airflow sensor (MAF sensor) located approximately in the middle of the hose, between the air filter box and the engine?
With a 4-pin connector?

Which diode ???

Thank you.
Ann.

Exactly, a 5-pin connector where only 4 pins are used ;o).

Please refer to the articles on 'Diode' and 'Mass Air Flow Sensor' for more information.

It explains everything very clearly, which was very helpful and saved me 85 euros.



Regards,
Alex.

Hello.
I have an Audi A4 2.5 TDI V6 B5.
I'm experiencing the same problem with the LMM again. I replaced the first one, and then the performance was back to normal.

'Recently, I've been experiencing the same power loss again. Suddenly, the engine isn't revving past 2000 RPM (regardless of the gear).'

I heard that for the small engines of the VW group, specifically the 1.9 TDI, there's an alternative Mass Air Flow (MAF) sensor to the Bosch one. Apparently, Pierburg (formerly of DaimlerChrysler) makes one.

If someone has the replacement part number for the correct mass airflow sensor...
I would be very grateful if you have information for a 2.5 TDI from Pierberg (DC) !!!

P.S.: My key numbers are zu.1 010226 and zu.2 0588.

Hello,
I think it's the N75 solenoid valve, which controls the turbocharger boost pressure, because the lack of power and pulsating acceleration suggest that.
Have a nice weekend.
Best regards, Thomas.