A4 2.5 TDI BDH 180 hp smokes under load and at idle

Hello everyone,

My car has been emitting a lot of smoke recently, both under heavy load and when idling.

I performed a log drive, and it shows an average of 250-300 mg less air mass (despite the boost pressure being within the target range) compared to a log drive I did a few weeks ago. I've attached the file.
However, I didn't rev it up too high because it was making some strange noises in the higher RPM range, which is hard to describe, but maybe like a slight rattling sound (!?!).
I initially suspected the turbocharger, but as long as it's building full boost, it can't be the cause of an air shortage... right?
Here's what I've already investigated:

- The radial play of the turbo seems to be okay, maybe slightly increased, but I can't really judge. Axial play not perceptible.
- No excessive oil accumulation in the charge air duct.
- The VTG (Variable Torque Generator) is functioning correctly and tightens properly during the actuator test.
- Vacuum hoses are sealed.
- The VTG pressure vessel maintains the vacuum.
- The AGR pressure sensor also maintains the vacuum, and the valve makes a distinct clicking sound when released.
- LMM temporarily replaced with a new one for testing.

"Something curious I noticed is that I once performed an EGR valve actuator test. The moment the valve opens, the smoking stops."

Best regards and many thanks.
Tobias.

Hi.

Okay, take off the valve covers and check if any of the camshaft lobes have lost one or more roller rocker arms.

I'm familiar with this from my (fortunately) former boyfriend's Passat 3BG.

Hello,

It's also important to consider the color of the smoke. Black smoke indicates insufficient air, a faulty EGR valve, or worn camshaft lobes. Blue smoke suggests that engine oil is being burned, which could indicate mechanical damage to the engine or turbocharger.

Best regards, Rainer.

Hi everyone,

Okay, I would say the smoke appears more black, which would also be consistent with the lower air mass. I checked the older logs again, and there's a difference of 400 mg at 3000 RPM. I've attached the old log file.
How likely is it that the EGR valve is defective, despite significant resistance when inhaling and a noticeable clicking sound? Could the noise at higher RPMs be caused by an "fluttering" EGR valve? Has anyone ever heard of something like that?

Hello,

Just because it clicks, it doesn't necessarily mean it's sealing properly.
I can't tell you anything about the statistical values, but unlike my wife's A3, your car is much easier to disassemble and inspect.
Camshaft problems would also be typical for that engine, see also the comment from @Rüdi;

Best regards, Rainer.

Okay, here's a quick update.

"The turbo is still okay for now... The exhaust side isn't oily, but the variable turbine geometry (VTG) makes a slight clicking sound about halfway through its range when I manually operate the lever..."
The AGR valve also makes a good impression... I'll try sealing it up for now and install a different charger instead...

Hello,

Older loaders tend to produce white-blue smoke. If the amount of air being drawn in under full load is incorrect, I would check the EGR valve and pressure test the intercooler system for leaks.

It is the lack of intake air during combustion that causes the black smoke.

Best regards, Rainer.

Okay, I've now declared him legally dead. I drove it again, and there's a metallic ticking sound coming from somewhere, and it smells like oil and coolant. R.I.P.

-_-

Too bad, thanks for the feedback!