VW Passat: Reduced Performance After Heavy Rain?

Hello everyone in the forum,

Perhaps one of you might be familiar with this problem and can help me, because the workshop is completely stumped!

I've already read through several threads, but it's not the same problem as in the other posts... ;-(

This June, I was driving in heavy rain again, and sure enough, the mass airflow sensor broke (for the second time - the first time it was replaced). The performance was severely reduced, and I could barely make it home at full throttle with a speed of just 120 km/h.

The next morning, my car started and ran almost 'like before.' Since then, I've noticed a significant 'shift' in the torque curve, which now kicks in around 2600 RPM instead of the previous 1900 RPM. The usable rev range has noticeably decreased. Furthermore, the maximum power is lower; on a flat road, the speedometer only shows 'just' 200 km/h. After various test drives with other Passats from the dealership, this was now confirmed to me.

However, the most significant drawback is that my average fuel consumption has increased by almost 1 liter per 100 kilometers! Since I drive almost the same routes (mostly highways), these values can be easily compared.

The readings from the mass airflow sensor are fine, as are those from the turbocharger. The measurements were taken using the standard method at the VW workshop, at 3000 RPM.

The car: Volkswagen Passat, manufactured in 2001, with a PD engine and 96 kW of power, no modifications.

Does anyone recognize this problem? Has anyone had similar experiences?
Unfortunately, I'm not a 'tinkerer' myself - do you have any tips?

Thank you very much and best regards!

Andreas.

While I don't know anything about PD (presumably referring to a specific system or technology), your description sounds almost like a change in the fuel injection timing (with symptoms such as reduced maximum speed, shift in torque curve, and high fuel consumption).

With the AFN, you could check the pump; I'm not sure if that's possible with the PD.

Hello,

Do you still have the data from the measurement run? If so, please post it here. Unfortunately, it's a common experience in this forum that many VAG workshops do not adhere strictly to the specified conditions. The same applies to the error memory: Unwanted errors are often simply "cleared" quickly.

Hi.
especially @ Michael II as the "Data Pope" .

The PD engines still seem quite mysterious to me compared to the VP-TDIs, especially regarding the relationship between observed symptoms and actual causes.

PDs (Positive Displacement pumps) are, in my opinion, simpler regarding their design than centrifugal pumps (VPs): they don't have any injection adjustments with all the associated components, no flow control valves, and no feedback loops for regulation.

However, it seems to me that diagnoses for faults in variable valve timing (VVT) engines are easier to perform and, above all, more understandable!
How does that all fit together? Or am I completely misunderstanding everything?

Hi and thank you very much in advance.

I called the workshop and they told me:

The error reading process did not reveal any errors.
Diesel filter replaced.
Air filter replaced...

They're saying that the torque should be back now. I'll pick up my car tomorrow and let you know how it goes.

Michael: I could get the measurements; they're available in the workshop.

'Thank you!!!'

Andi.

Hello Ulf,

I don't believe that troubleshooting problems with PD engines is generally more difficult. Rather, what's lacking is the years of experience and experimentation with this technology. This is also quite noticeable in workshops.

Workshops are still having problems with the old Motronic system .

My salesperson mentioned that regarding the mass airflow sensor (MAF), they changed the air intake path to the filter box after the problems became known. Previously, it drew air in behind the front grille; now, it draws air in from the left fender liner, outside of the splash zone.

The reason for this was that too much water being sucked in during heavy rain or a long highway drive ended up in the splash of the front tire, which damaged the mass airflow sensor (MAF).

Sounds plausible.

CU Gremlin.

Hello. I had the same problem with my A6 2.5 TDI. I replaced the air filter (MAN aftermarket part). After a rainy drive, the mass airflow sensor (MAF) failed three times. I switched to an original VAG air filter, and the problem was solved.