VAG-COM Diagnostics: Help with Data Analysis

Hi fellow mechanics,

As some of you may know, I'm having some issues with my Audi V6 TDI (MBK AKN) from the year 2000 (it's making quite a loud knocking noise).
I downloaded the list of target values and performed a measurement run, but some of the values don't quite match. Perhaps one of you experts can offer some insight?

The values are located here: www.mzone.de.vu/audi/werte.xls

The yellow columns represent the measured values.

Thank you all in advance!

M.

Hello,

I'm not a V6 specialist, but first, I would check the valve timing.
Were any repairs or maintenance performed on the control unit shortly before the error occurred? Were the timing belt and tensioner in good condition, and were the pulleys securely fastened?

Best regards, Rainer.

No, no work was done on the control unit! I had a new mass airflow sensor (MAF) installed 2 months ago,..... but the increased fuel consumption was a sign of that .

I've been to the workshop several times because something doesn't seem right, but they're now starting to think I'm crazy.

M.

"Could you please check the valve timing and the position of the pump drive?"

Thank you, Rainer.
I'll probably have to get it done at a workshop, or is it something I can do myself?

Hello,

If they haven't found anything in the workshop so far, I don't think they're particularly motivated.
I'm afraid this is probably a waste of time. Either you check it yourself, or have it inspected by another workshop.

Whether here.

Audi A4 and Avant (diesel models).
1.9-liter TDI diesel / 2.5-liter TDI diesel (66/81 kW, 90/110 PS with injection pump/nozzle). (Tb)

MOTORBUCH PUBLISHING HOUSE

etwas brauchbares zur Überprüfung der Steuerzeiten drinsteht, bin ich überfragt. So"would like to..."
The method is actually always the same:
- Align the crankshaft to the top dead center (TDC) of the first cylinder, which can be verified using a pin in the clutch bell and markings.
- Check camshaft position.
- Check the position of the drive gear of the injection pump.

Best regards, Rainer.

I'm going to take another measurement tonight, just to be sure.
Okay, so I'll be going to Nuremberg tomorrow and to the workshop on Tuesday!

Here's the translation:

'One more question about the individual values:'
Operating state:
Desired: 00100
Actual: 00101
Keyboard setting: Injection start valve - desired (load) 50..95, actual 42.6.
Intake manifold pressure in mbar:
Target: 1850..2250, Actual: 1550.
Smoke emission limit (in mg/H): target 39..47, actual 30.1.

Can we draw any conclusions from this?

M.

merlin wrote:

Here's the translation: "One more question about the individual values:" Operating state: Desired: 00100 Actual: 00101 Keyboard setting for injection start: should (load) 50..95, is 42.6. Intake manifold pressure in mbar: Target: 1850..2250, Actual: 1550. Smoke emission limit (in mg/H): target 39..47, actual 30.1. Can we infer anything from that?

Hi.

I'm not familiar with the operating status.

However, vacuum leaks and excessive smoke suggest a potential loss of power due to issues with the mass airflow sensor (MAF) or turbocharger.
Of course, only if you were driving at full throttle during the measurement.

Okay, I took another trip and got some new readings. The values that are outside the tolerance range are marked in red again!

www.mzone.de.vu/audi/values1.xls


The amazing thing is that the start of injection (Block 0, Field 2) initially read 70! Then I briefly pressed the accelerator and returned to idle, and it jumped to 108!
Now I really don't understand anything anymore.

M.

The situation is relatively clear to me. Operating state 00101 is normal. This simply means that, in addition, the magnetic coupling of the air conditioning compressor is also engaged.

The values for the injection start clearly indicate that your fuel injection pump is significantly delayed. With a value that far off, the electronics should normally switch to emergency mode. In this case, the ESP light would occasionally illuminate, and the engine power would be significantly reduced to prevent damage. Please check the injection timing control range. However, there is no information about this in the book mentioned above... (There is very little information about the V6 engine in that book, not even how to check the valve timing!)

A short guide:
-Engine idling.
-Initiate setting 4.
-The solenoid valve for injection start is now alternately opened and closed for 10 seconds.
-Monitor display fields 2 and 3:
bei Anzeigefeld 2= früh muß 3 größer als 14° v. OT sone
When display field 2 indicates 'late', value 3 must be less than 0° relative to the origin (OT).

If the values deviate, it indicates either an incorrect injection timing or a clogged regulator.

@vikinger THANK YOU - I'll check it out tonight!
However, I have one more question: In the basic settings, which block should I select?
You are writing '2' emails from 'ANzeigefeld 2'. Could it be that there's a mistake, and it should be '2' or '3'?

Thank you for your help.

M.

However, I have one more question: in the basic settings, which block should I choose?
You are writing '2' emails from 'ANzeigefeld 2'. Could it be that there's a mistake, and it should be '2' or '3'?

M

No, that's correct as is. As I said, the adjuster now controls both extremes, alternating every 10 seconds. So, the engine is idling, and the value in display field 2 changes every 10 seconds to 'late' or 'early,' and you observe the corresponding value in display field 3.

Okay, I've just started logging, here are the values:

www.mzone.de.vu/audi/early_late.xls

Interestingly, when it's cold in the morning, my engine doesn't rattle as much, and it even sounds quite pleasant!

Thank you.

merlin

'These values are perfectly fine. So, either the injection timing valve is defective, or the injection pump is significantly delayed, although I'm leaning more towards the latter. Just try adjusting the pump a little bit towards earlier timing (when viewed from the direction of travel, that would be to the right). To do this, you only need to slightly loosen the three screws on the camshaft wheel until the drive wheel of the pump timing belt is movable, and then turn the pump shaft to the right. (But be careful: The screw on the pump shaft must not come loose!)'