AFN Engine: Sudden Power Loss Troubleshooting

Since I posted my problem in another thread previously and didn't get much of a response, I'm trying again here in my own post.

Seat Ibiza, manufactured in 1998, 1.9 TDI engine (AFN), 110 horsepower, 205,000 km.

Approximately 2 weeks ago, the Ibiza experienced intermittent power loss for 2-3 days (including while driving, with an 'on-off' symptom). Since then, the power issue has been constant.
It all happened after I replaced the three engine mounts (suspension). I'm not sure if it's related.

The maximum speed is reached at approximately 100 km/h after 2-3 minutes of acceleration. When the accelerator pedal is fully pressed, the vehicle seems to develop less power (at approximately 0.5 bar), compared to when driving with approximately 50% throttle (at approximately 0.3 bar). (Is the turbocharger consuming more power than the fuel injection system can provide?) Overall, the car feels like it has 40-50 horsepower. Important: There are no entries in the error memory! (unfortunately!)

Following the instructions in the forum, I made the following logs: MWB (engine data) readings 1, 8, and 11, recorded at full load in the 2nd and 3rd gears, and again in the 1st, 2nd, and 3rd gears at full load while going slightly uphill. (It doesn't go beyond 3000 rpm; even in 1st gear, the power ends there). What I've noticed is that the air mass decreases as the engine speed increases. Shouldn't it increase instead?

The following items were also tested:
In MWB 7, the temperatures are the same at 2 degrees when the engine is cooled down.
In MWB 10, the charging pressure and exhaust back pressure are equal to the decimal point value when the engine is stationary.
In MWB 10, the pedal position remains stable at 100% when the accelerator is fully pressed.
In MWB 6, both brake switch bits change state simultaneously, and the clutch engagement is indicated.


Today, I tested the catalytic converter for defects (symptom of decreasing air mass with increasing RPM) by disconnecting the pipe directly behind the turbocharger. Unfortunately, no effect was observed (only the turbocharger whistled loudly from the engine compartment).

'Today, while driving to work in the rain, I suddenly experienced the conventional power mode for about 20 seconds. Just as quickly as it appeared, it disappeared. My suspicion is that humidity might be affecting the behavior of the mass airflow sensor (MAF). What other defects could this incident, caused by humidity, indicate? Could it be a short circuit or a broken cable (-> without leaving any error codes in the memory)?'

I read that the mass airflow sensor (MAF) is not very resistant to vibrations. It's possible that it was damaged during the removal process and while it was being stored in the workshop.

Unfortunately, I've run out of ideas. Can anyone else offer some help?


EDIT: With the 10-cent tuning, you can unlock more power from the car. So, it doesn't seem to be a problem with the fuel injection system (air in the lines, diesel filter, filter in the tank, pump failure, etc.).

Okay, since I'm impatient and probably belong to the tiny fraction of this forum that still drives vehicles from before 2000, and therefore didn't get an answer, I just used the 'brute force' method and connected a 1N 4200 diode between the MAF sensor signal and +5V.

Since I have to consider spending 100 euros on an oxygen sensor not only because of my budget but also because of the vehicle's manufacturing year, I only have one final question:

Assuming a constant throttle position, does the missing mass airflow sensor (MAF) affect the long-term durability of the vehicle? (Aside from the possibility of damaging the turbo by running it at full throttle in the lower RPM range).

Best regards, and have a good evening.
Peter.

Hello Neubaupe,

The diode LMM should not affect the durability, except for the soot (and thus potential VTG and intake clogging issues).

But it's not pleasant for the person behind when changing lanes, and it could cause problems during the next inspection.

Regards,
Guste.