Ignition timing deviations, injection deviations, 2.0 TDI BMM

Hello everyone,

I've been reading various articles about this topic lately. Well, I wanted to find out how it applies to my car, since it now has over 178,000 kilometers on the odometer.
Okay, so I created a log with the following data points: MWB 013, 018, and 023. According to my log, the fuel injection deviation and the magnetic valve readings should be within acceptable ranges.
So far, so good. However, I've now noticed the values for the switching time deviation. According to VCDS, these should be in the range of +100 to -100.
My results are tending towards a value of around -100. So, I tried to find out what exactly high negative values mean, but unfortunately, I couldn't find any information on that.

So, my question is: what conclusions can be drawn from these values? Is it generally better if the values are in the positive range, the negative range, or closer to zero?
What should I expect in my case (e.g., upcoming repairs? replacement of components?)


"The log was recorded at approximately 80°C coolant temperature, while idling. The fuel filter and engine oil were changed 500 km ago."


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

"MFG" stands for "Mit freundlichen Grüßen," which translates to "Sincerely" or "Best regards" in English. It is a common way to end a formal letter or email.

Okay, so high negative values indicate a fuel shortage. Since you recently replaced the fuel filter, we can probably rule that out as the cause.
"With our BMM (boost pressure measurement), I've always been able to increase the values by about 20 points with a new filter. When the values then became extremely negative and slight misfires were noticeable under full load, I simply replaced the PD wiring harness. That initially brought the readings back down towards -70."
Furthermore, sealing the components in the head could be an option, or a tandem pump.
But as long as you don't have any issues with the way it drives, I would just observe and not do anything about it yet.


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

"MFG" stands for "Mit freundlichen Grüßen," which translates to "Sincerely" or "Best regards" in English. It is a common way to end a formal letter or email.

Immediately before the start of the injection process, the solenoid valve at the pressure enhancement device (PDE) is activated. This creates a magnetic field that closes the solenoid valve, and the needle strikes its seat on the opposite side.

This point is the GDP.

Now the plunger moves downwards, and this is the point at which pumping begins.

In the engine control unit (ECU), the time required for the valve to open after being triggered is monitored by observing the current flow of this solenoid valve. This information is used to determine the optimal timing for the next injection event. All of this information can also be found in document SSP 209.
This only works within certain tolerances, specifically from +100 to -100. If the intake pressure is not reached, the fuel in the combustion chamber becomes too hot and vapor bubbles form.
The valve needle now has less resistance and closes faster. As a result, the MWB 23 device will display higher negative values. In this case, it will be for all cylinders.
Or, conversely, a blocked pore can be difficult to clear, and it may take the needle a long time.
Then high positive values will result. This is noticeable because it only affects the defective PDE.
For the engine in question, negative values between 60 and 80 are normal because it is equipped with pump-injector units that use fast-acting solenoid valves.
These are necessary to enable post-injection in vehicles equipped with a diesel particulate filter (DPF).

PDEs 1.1 and 1.3 from the 1.9 version, on the other hand, are slower.

In the uploaded log file, the BIP (Battery Information Panel) readings appear normal. However, the value "128" in field MWB 18 at the very bottom is not correct. This brings us back to the possibility of a wiring harness issue.

Is it running smoothly?

Hello,

First of all, thank you for the excellent explanation. It's really very well explained and easy to understand.
I had read that the value of 128 for the MWB 18 would be acceptable at the time of starting.
Basically, it seems to be running fine so far. There are just a few things that I've noticed since I started driving the car.

- He only achieves his top speed with great difficulty. Most of the time, he doesn't exceed 200 km/h, according to the speedometer.

- Mir ist letztens ein sehr merkwürdiges Verhalten aufgefallen. Es kann allerdings sein, dass es ein rein subjektives Empfinden von mir ist. Und zwar kam es mir vor, dass wenn ich den Wagen ganz langsam beschleunige ( bei ca. 50kmh im 5ten Gang ) der Wagen von selbst "Vollgas" gibt. Das ganze muss man sich vorstellen, als wenn man das Gaspedal ein kleines bisschen durchtritt, der Wagen aber ganz kurz Vollgas gibt, das Gas wieder wegnimmt und wieder das ganze von vorne. It feels like it doesn't even take a second.

Do you think I should consider replacing the wiring harness for the PDE elements?
If I were to assume that the problem is related to the wiring harness, what changes would one be able to observe if I replaced it with a new one?

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

"MFG" stands for "Mit freundlichen Grüßen," which translates to "Sincerely" or "Best regards" in English. It is a common way to end a formal letter or email.

I meant the value of 128 at the end of the file. But it seems like the motor was already off by then. In that case, everything is fine.
The meaning of these numbers is explained here: /viewtopic.php?t=16802
The problem you described has nothing to do with the PD cable harness.

Um, yes, I forgot to stop the log before shutting down the engine.

Yes, so problem number 2 actually occurs very rarely; at least, I've only noticed it twice so far.

I'm wondering what benefit there is to reducing the negative switching time deviation, perhaps by using a new wiring harness.

Nothing. Your wiring harness is not currently damaged. And the timing must be set like that for this engine.

Steffen W wrote:

Nothing. Your wiring harness is not currently broken. And the timing must be what it is for that engine.

Okay, then I'm relieved for now.

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

"MFG" stands for "Mit freundlichen Grüßen," which translates to "Sincerely" or "Best regards" in English. It is a common way to end a formal letter or email.