AFB Motor Failure: Troubleshooting & Repair

Recently, I had my Audi A4 2.5 TDI V6 tested on a dynamometer. The results were:
112 horsepower instead of 150, and 280 Nm of torque instead of 310 Nm.
The verdict from the friendly experts: used camshafts.
Compression pressure: 4 x 24 bar.
2 x 22 bar.

(New: 27-33, Shelf life limit: 23)


The engine runs very smoothly.
Here's how I would ask a question: Could measured values cause such a significant loss of power (38 horsepower)?

Rafael.

RAF1 wrote:

This is how I would ask a question: could measured values cause such a significant loss of power (38 horsepower)?

I'm not sure how lost cash and horsepower relate to TDI engines.

The measured loss of "only" 10% torque (at 2000 rpm), but 25% peak power (at 4000 rpm), seems to me to be consistent with the likely shortened valve opening times or reduced valve lift caused by NW (Normal Wear) wear: Both of these factors hinder the gas exchange most significantly at high engine speeds.

Therefore, I believe that the diagnosis is likely correct.

But there are also other causes of compression loss.

Hello Rafael,

It's possible, but I think it's very unlikely that the motor has so little compression due to wear. (Possibly the camshaft).


Here, there was a discussion about compression measurement and blue smoke. At that time, VW had already diagnosed a problem with the engine. (It was a faulty measurement).

What all has already been done to your car? I'm reading about engine control units and nozzles.


Has the valve cover ever been removed?


Greetings.

Rainer.

So many tests were performed, and so many incorrect diagnoses were made.

AGR deactivated, components temporarily replaced for testing: engine control unit, fuel injection pump, turbocharger, turbocharger solenoid valve, fuel injectors.
The LMM (likely referring to a Lambda/Mass Air Flow sensor) consistently shows too low readings. It has been replaced four times in the past two years (e.g., at 3000 RPM, it reads 780 instead of 870). It has been replaced four times in the past two years.
Intake manifold checked for leaks.

Interesting fact: when connected to the external box, the dyno test showed 150 horsepower and a maximum torque of 363 Nm.
(without Box 112 hp, 280 Nm)
Greetings.

Rafael.

RAF1 wrote:

So many tests were performed, and so many incorrect diagnoses were made... AGR deactivated,

temporarily replaced: engine control unit, fuel injection pump, turbocharger, turbocharger solenoid valve, fuel injectors. }
... but have you ever taken off the valve covers and just quickly checked the NW (narrowing)?
Why? Are they installed in your car in such a way that you have to remove the engine first?

The camshafts have slight wear marks on the lobes, but it doesn't look too bad.
The technicians checked the cylinder sealing with a knife – and found it to be okay on all cylinders.

Rafael.