Performance Issues at Full Throttle

Hi.
I'm having a problem: I'm experiencing brief power interruptions whenever I press the accelerator pedal. Could this be related to the turbocharger boost control, or is this normal? I've attached a graph for reference. It's an Octavia with a TSI engine.

http://www.alexvr6.de/Bilder/grafik.gif

or as a link (larger image).

http://www.alexvr6.de/Bilder/grafik.gif

See the range from 122 to 155; could this possibly be the mass flow rate?

Best regards, Alex.

Since the boost pressure, according to the image, is constantly being adjusted up and down.
Let's check if the vacuum hoses are in good condition and if the VTG (Variable Turbine Geometry) is operating smoothly.


Maybe check the fuel filter as well! It might be clogged and not providing enough fuel under heavy load.

"In my case, the solenoid valve on the 1Z was stuck, which caused the boost pressure to collapse completely when accelerating hard, and then suddenly spike back up."

Besides the boost pressure, what I've also noticed are the mass airflow sensor (MAF) values.
They twitch in rhythm with the boost pressure. Possibly a faulty mass airflow sensor (MAF sensor)?

Hi AlexTDI!

It's great to see another owner of a car with an AGR engine in the forum.

@Steffarn:
While the AGR is a 038 engine, it is unique among its kind because it still features a wastegate turbocharger!

Now, regarding your problem. Your mass airflow sensor (MAF) value is dropping significantly before the "erratic behavior" starts. Therefore, you should definitely try cleaning the MAF sensor or use the "diode fix" (see search function) to rule out a failing MAF sensor.
It seems your main problem lies elsewhere. I suspect the N75 valve (magnetic valve for boost pressure control) might be causing issues and generating significant boost pressure fluctuations. Try a test drive with the connector unplugged. This will disable the valve, and the boost pressure will be limited to approximately 0.6 bar (the valve will then be fully open, and the boost pressure will be applied to the pressure sensor on the turbocharger without any modulation). If the engine then runs properly, aside from the loss of power, then I would recommend replacing the N75 valve.
Okay, when you unplug the connector, you will of course get an error message, but you know the origin of the error, and you can naturally clear it using VAG-COM .

A loose connection on one of the sensors (boost pressure, mass airflow sensor, N75) could also cause this type of error, but it's very unlikely, especially since, if I understand correctly, your problem always occurs reproducibly under full load within a specific RPM range?

Regards,
Alex.

offtopic

@donalexo: there's more to the AGR here, I have one in a 2000 Octavia .

Thanks for the answers so far...
I won't exceed the mileage limit, I still have a used car warranty.
Okay, I'll check the solenoid valve. It's not just happening under full load; in the picture I showed you, it occurred while accelerating on the highway.
After driving for a long time on the highway and then getting back onto a country road, I feel like the car isn't pulling properly.
I've only been driving my diesel for 8 weeks, so I don't have much experience with it yet. I'm more familiar with VR6 and G40 engines (which are gasoline engines).
Best, Alex.

Here are the two log files from VAG-COM:
http://www.alexvr6.de/Daten/log.rar

Try swapping the MAF sensor with a diode. In cases of 'power loss' (which might be similar to a brief hesitation when accelerating, typically between 2,300 and 2,700 RPM), the MAF sensor is often faulty in pump-injector engines and needs to be replaced. After that, you'll see how well a TDI can accelerate. By the way, will an error code appear? Will the car still reach its maximum speed?

Best regards, WarLord.

Drehzahl ist bei mir etwas höher , das ist wie wenn man vom Gas geht und gleich wieder drauf tritt. Ist aber nicht immer , heute war es mal ganz schlimm , da hatte ich probleme über 170 (Tacho) zu kommen. Vmax macht er noch , ist ja nicht immer Vmax Tacho ist 205 und Vmax VAG-COM ist dabei 188. Im Schein steht ja 180 drinne. Ist mir bis jetzt auch nur im 5. Gang aufgefallen. I'm really at a loss.
Best regards, Alex.

Hello,
I experienced a pulsating sensation when accelerating at full throttle, starting around 3000 RPM.
It was happening roughly every 2 seconds, as if the engine was switching between 80% and 100% power. Unfortunately, I haven't completely solved the problem yet, as I'm also missing the maximum speed. It might be related to the mass airflow sensor (MAF).
By the way, the new valve is working properly when idling. So, the old one was definitely defective.

The part is called a 'magnet valve' by the VW parts department. You can find it on eBay. The part costs 30 euros new. The part number is 028 906 283 F.
Best regards, Thomas.