A4 2.0 TDI Germany: Runs poorly during regeneration + fuel level sensor issue

Hello everyone.

Also folgendes Problem: Ich fahre ganz gemütlich auf der Autobahn und meine Restweiten anzeige sagt ich komme mit dem Tankinhalt noch 500km weit. Keine 2 Kilometer weiter > Ich fahre von der Autobahn ab, Fehlen mir auf der Restweiten anzeige 20-50kmobwohl ich einfach nur von der Autobahn runtergerollt bin?! Die fehlenden Kilometer kommen dann in der Regel nach 1-3 Minuten wieder zurück: Wohlgemerkt der Durchschnittsverbrauch blieb die ganze Zeit gleich. 2. Problem> Wenn der Motor in dir Regeneration geht läuft er wie ein Sack Nüsse. SWhen idling, it sometimes experiences intermittent misfires, and acceleration is jerky or uneven. However, once the regeneration cycle is complete, it runs smoothly again like a kitten.

So meine Schlussfolgerung ist nun Folgende: Mein Vorbesitzer ist Ewigkeiten mit einer Defekten Tandempumpe rumgefahren welche ja bekanntlicherweise Motoröl in den Dieselkreislauf einträgt (Bei Defekt). Das die Vorförderpumpe nicht mehr 100% Druck aufbaut und der Tankstandgeber auch einen Weg hat weil alles mit Öl versifft ist. Den ich kann mich noch erinnern wo ich die neue Tandempumpe eingebaut habe das er, obwohl ich mit VCDS die Vorförderpumpe angesteuert habe schon ein welchen gebraucht hat er alles Luft aus den System war. Before I spend 470 euros at Audi on a new unit consisting of a pre-lift pump and fuel level sensor, I thought I'd ask here first.

The DPF has a loading of 13.65 grams. When we last read the PDE values, sensors 1 and 2 showed +0.10-0.30 mg/H, while sensors 2-3 corrected to negative values after a few seconds, also within the range of 0.10-0.30 mg/H. What pressure should be reaching the diesel filter at the front, coming from the pre-filter pump?

Thank you for your help.

Hello,

The fuel gauge is probably not failing due to an oil supply issue. More likely, you have a loose connection or faulty wiring/connector to the sensor, or the sensor itself is defective.
A loose cable won't be fixed by replacing the sensor.

A diagnostic scan would have been helpful to check for other potential issues, such as problems with the power supply voltage for various sensors.

PDE idle speed control, very good values; the permissible range is up to a maximum of +/- 2.5 mg/h. I see correction values of +/- 2 mg/h, which are "not ideal but still within normal limits."

To test the pressure of the pre-lift pump, there should be some information in the motor's repair manual. There are also several related topics available; see the search results and similar posts.
Ich kann den Inhalt dieser URL nicht abrufen und übersetzen. Bitte gib mir den Text, den du übersetzt haben möchtest.
/viewtopic.php?t=27191&highlight=tandempumpe

Best regards, Rainer.

Hello diesel mechanics,

I just bought access to Erwin (siehe Fehlerdatenbank) for 8 euros and downloaded all the relevant guides, which I've been studying. While I now know how to test the pressure at the tandem pump and how to electronically test the pre-charge pump, nowhere is it indicated what pressure the pre-charge pump needs to deliver to the tandem pump. (No wonder why Audi workshops are often clueless themselves.)
Your second link was interesting, though. Regarding the potential leaks in the cylinder head. I sometimes also have blue-white smoke coming out of the exhaust. As soon as I have access to VCDS again, I'll do a car scan.

Hi,

Sorry, I only have the values listed in my linked topic for the print settings. If your values are similar, it should probably work.

Best regards, Rainer.

Okay, the car is still running, but I haven't been able to address the problem yet because I don't always have access to VCDS.

Since there's a planned regeneration section coming up in a few kilometers, I'd like to try and record some data during that stretch. What values should be recorded to help pinpoint the problem areas?

I was thinking about the following:
- Speed/Revolutions per minute (RPM)
- Boost pressure IS
- Desired boost pressure:
- Control of the charge pressure regulating valve (Possible leaks in the vacuum system?).
- Lambda value (possibly due to carbonized PDD nozzles?)
- Differential pressure

My thought: Is the problem related to the fuel injection system or the turbocharger/intercooler system?

Hello.

Quote:

Poor performance during regeneration + fuel level sensor issue

I'm not really sure which values should be logged from the engine to diagnose this problem.
If the remaining range fluctuates significantly despite a roughly consistent average consumption, the problem is likely with the sensor or its wiring.

And if the engine is running poorly during regeneration, it's likely that it won't run significantly better otherwise either?

Best regards, Rainer.

I've already checked the pre-pump, and everything seems to be fine on that side (it only needs 0.5 bar of pressure for the diesel to reach the tandem pump without air bubbles). And I can live with the fuel level sensor...

"But you're right, it could definitely run better. The other day, I did a logging session without any regeneration occurring. I noticed that the actual boost pressure is always lagging behind the target boost pressure by about 0.2 to 0.5 bar."


My guess is that when it goes into regeneration mode and everything around the charger gets hot.
- Either the loader itself is malfunctioning, or it's a problem with the VTG (Variable Transponder Generator).
- A vacuum hose.
- or the DPF creates too much back pressure.

Unfortunately, I'm still waiting for the system to regenerate so I can start logging data.

Hi.

Quote:

- Either the loader itself is malfunctioning, or it's a problem with the VTG. - A vacuum hose. - or the DPF generates too much back pressure

.
You are correct. Please also check during normal operation whether the target pressure for the turbocharger is being reached. If it's difficult to achieve, additionally inspect the intercooler system for leaks, in addition to the points you mentioned.
Since a higher boost pressure is used during regeneration in partial load conditions, these problems become more noticeable, which could explain why the car performs particularly poorly during regeneration.

Best regards, Rainer.

Hello,

For the typical pressure differences observed in the DPF (Diesel Particulate Filter), there's a topic with empirical values available.
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.

What amount of ash, either by mass or volume, does the control unit indicate is present? Usually, it only becomes critical when it's significantly over 200,000 km.

Best regards, Rainer.