Again, problems with V6 TDI engine: knocking, smoking, low power

Hi everyone,
Perhaps some of you remember me; I've had problems with my A4 before --> details:
Audi A4 (B5) Avant 2.5 TDI quattro - Engine code: AKN - Year: 2000 - 150 HP.

At that time, my mass airflow sensor was broken - in addition, the engine was making a knocking sound, like an old Hanomag,... but that all stopped suddenly!
Meanwhile - I've continued to put a lot of money into the car, ... but okay!
New problem:
Sometimes very little power, extreme misfiring when cold, even when warm it still misfires heavily, no sign of the smooth running of a V6 engine. Sporadically, between 2000 and 2700 RPM, there are very strong vibrations... The error memory is empty! Lmm is okay!
I'm just not sure what to do next. I've even considered that the pump might be defective, but replacing it would be expensive.
Perhaps you could give me some more ideas to think about?
Many thanks to everyone who takes the time and effort!

Markus.

Food for thought: When it comes to nailing things down, I'd like to take a look at the values for the injection start time.

Best regards, Rainer.

Okay, I've just finished taking some measurements.
Here are the values:
www.markus-merk.de/audi/data.xls

What do you think about that?

VG

M.

Hi,

A highly discussed candidate is also the tensioner pulley for the ESP (which would also align with Rainer's post regarding adjustable valve timing). Please check if your engine is subject to the regular inspection requirement for the tensioner pulley. The service manual should also indicate when it was last tightened. Michael II posted the engine number ranges of the affected engines somewhere. Just search for AFB and AKN.

hi marco,
Perhaps you mean this thread.
/viewtopic.php?t=131&highlight=tensioning_roller

but that's about the tensioner for the timing belt, not the belt for the ESP – or have I missed something?

Oh yeah, and one more thing... I checked the service manual, but unfortunately, there's nothing in it. Also, the car only has 65,000 km (approximately 40,000 miles).

Best regards and thanks to everyone.

Markus.

The timing belt runs around the crankshaft and the fuel injection pump, among other components. Water pump, camshafts (the AKN engine has four of them, as far as I know), and possibly the oil pump.

Best regards, WarLord.

@ warlord

It did not go unnoticed by me... which components does the timing belt run on )?
If I'm not mistaken, the pump has its own belt.

Unfortunately, this doesn't bring me any closer to solving the problem!

Greetings.

M.

Hello,

I meant the ZR (zero-risk) for the NW (Northwest), sorry. By the way, the AKN engine has two timing belts.

so, I've taken some measurements.
Here are the values:
www.markus-merk.de/audi/data.xls

What do you think about that?

VG

M

Hi Merlin,

What kind of measurement run was that? It doesn't look like a VAG-COM log. Please post the correct log!

Hi Marco, these are excerpts from the log. I only imported the :-)target data sheet from Rainer into Excel and adjusted the columns.

@merlin and Marco

Thank you for the clarification. I wouldn't have thought it had two. Is one for the left side and the other for the right side?

Best regards, WarLord.

Hmm, well, two individual measurements aren't really ideal; I was expecting something more like a measurement run...
The two measurements are correct, but whether that's always the case? "Spannrolle" is a good tip.
Based on the measured values, at least nothing should be knocking. Was something other than diesel possibly put in the tank? If one or more fuel injectors are faulty, it will likely also cause knocking. So, if you can't find anything and the problem doesn't go away even after the next refueling, it might be worth having the fuel injectors checked.

Best regards, Rainer.

Thank you for the reply!
hi rainer, why are there two measurement values?
In the Excel sheet, there are several values listed for both idle and under load conditions.
Could it be that the Excel sheet is not displaying correctly for you?
If that's not the case,... what do *you* envision when you think of a test run?
I've refueled several times since the problem started, but nothing has changed.
and of course, always the same one! Mistakes excluded!

Hello.

Okay, I've only found two data points for the injection timing: one at idle and one at full throttle. When does it knock? Also, what about idle speed?
I had actually envisioned going through the entire load range and recording the values.
I find it a bit insufficient to assess something based on a regulation that only checks two measurement points and doesn't even consider dynamic behavior like load changes.

Best regards, Rainer.

@rainer
Okay, you're right, sorry many times! 'It's making a cold knocking sound (likely a Russian tractor). It knocks when accelerating (even when warm), and sometimes it sounds like rattling.'
I took the car to the mechanic in the summer because of a loss of power and knocking/clattering noises.
The turbocharger boost control valve and the mass airflow sensor (MAF sensor) have been replaced (the MAF sensor, as usual, free of charge!).
Since then, the performance has been back to normal, and they had both valve covers open.
and we checked everything related to the rattling/knocking sound, but everything seemed to be okay.
Okay, so no visible wear marks or signs of running on the camshafts, or they are not worn.
Should I log the data for blocks 4 and 8 during operation with load switching and post it here?
I had also considered the possibility of a partially defective fuel injector.
How can I test this without a complete disassembly?
Regards,

Markus.

Okay, I have a new log under...
www.markus-merk.de/audi/log1.csv
That should be more informative!

I also checked all the fuel injectors with a metal wrench. Is it normal for some injectors to be louder than the injector with the needle lift adjuster? I always thought that the ones with the needle injector would be the loudest.

Thank you for your help.

Markus.