TDI Performance Loss: Causes & Solutions

Hello,

I drive a Skoda Fabia TDI with 74 kW, manufactured in March 2001, and it has 130,000 km on the odometer. I bought this car last fall and have been very satisfied with it so far.
Seit ca. Anfang diesen Jahres ist mir ein Leistungsverlust aufgefallen. Besonders bemerkbar war der schlechtere Durchzug und eine reduzierte Höchstgeschwindigkeit. Ich hab dann den LMM wechseln lassen. Die Durchzugswerte haben sich dadurch etwas verbessert, sind aber noch nicht wieder auf dem Ausgangsniveau und an der max. erreichbaren Höchstgeschwindigkeit hat sich nichts geändert. Zur Zeit sind auf gerader Strecke NUR 180 km/h möglich, als ich den Wagen gekauft habe waren ca 210 lt. TaCome in.
Since that seemed a bit insufficient, I drove to my mechanic's shop and had the error memory checked. However, there were no error codes stored.
Following this, a test run was conducted. During the test, the workshop supervisor noticed an elevated reading. All other readings were normal.

System default settings 11.

900 /min 989 mbar 0%
1410/min 1122 mbar 0%
1410/min 989 mbar 99%

The underlined value is approximately twice as high as it should be.
Since the workshop foreman himself didn't know what was causing this value, he called Skoda, but they were also unable to help him.

Can anyone give me a hint about what's broken with my [device/item]?
Is it dangerous to drive a car under these circumstances?

I noticed some damage to the insulation in the engine compartment. Could it be that a rodent or something similar damaged a hose?
However, during a visual inspection at the workshop, no defective hose was found.

Thank you very much.

Best regards,
Frank.

Hi Frank,



System default settings 11.

900 /min 989 mbar 0%
1410/min 1122 mbar 0%
1410/min 989 mbar 99%

The underlined value is approximately twice as high as it should be.


Was hat der Werkstattmeister den da geloggt? Boost pressure?


Since the workshop foreman himself didn't know what was causing this value, he called Skoda, but they were also unable to help him.


I'm happy to believe that, given the limited information available.


Can anyone give me a hint about what's broken with my

'Try to come up with a reasonable log that includes all the relevant parameters. The values you provided have no connection to reality and are therefore unusable. We have affordable adapters and VAG-COM devices available in our shop. If necessary, you can also have a diagnostic test performed by VAG. You mentioned that the insulation has been added. This means there's a relatively high chance that some vacuum or pressure hoses may have been affected. Please re-check them for leaks.'

During the measurement run, many values were recorded. I left the measurement report at home, and since I won't be back home until the weekend, I won't be able to post all the measurement data here until next week.

The hoses were subjected to a visual inspection, as previously described. Could the damage be so small that it is not easily detectable?

Best regards, Frank.

Hello,

I spoke with my mechanic's shop on the phone yesterday.

Regarding the measurement values:

The measurements shown were recorded while the vehicle was stationary and represent the boost pressure. All measurements recorded during driving are within the optimum range !

Regarding potential damage to the motherboard:

He said you would hear it if a hose was broken. He also checked the vacuum hose, and it's holding vacuum (he said that a valve opens occasionally, which means the hose is okay).

Regarding the driving experience:

The engine seems to function normally in the first three gears at speeds below approximately 100 km/h.
Bei Geschwindigkeiten über 100 km/h fehlt dem Motor die Kraft im 4./5. Okay.
In 4th gear, the engine starts to feel quite strained from 3400 RPM (approximately 140 km/h), and in 5th gear, the power output reaches its limit on a straight road at around 3500 RPM (approximately 180 km/h).
The fuel consumption seems to be too high even at speeds of 100 km/h (approximately 0.5 liters per 100 km).
The workshop foreman also noticed the lack of power during the test drive.

I plan to go to a different workshop next week.
What measurement parameters should be recorded during a test drive?

What other causes could be responsible for the lack of performance?

Note: I have been using 195/45 R16 tires (the standard size is 195/50 R15) since the spring of 1954.
mounted on the car.
Could this result in a speedometer discrepancy that could explain my problem?
'would'

[Translating...]

LMM ???

Hi,

Using the tire calculator, the following rolling circumference is obtained:
195/50/15 = 1757mm
195/45/16 = 1775mm

The deviation is only 1%.


All measurements recorded during the trip are optimal!


This statement is nonsense! If that were true, your car would be running properly! It's possible that the readings the mechanic recorded during the drive were optimal, but then he didn't look at the correct readings.



1410/min 1122mbar 0%
1410/min, 989 mbar, 99%

The underlined value is approximately twice as high as it should be.
Even this statement is nonsense. It shows absolute pressure, and if you subtract approximately 1000 mbar of atmospheric pressure, you can see that the turbo produces 112 mbar of positive pressure . Completely normal!
If the value displayed there were only half the actual value (666 mbar), then you would have a :arrow:underpressure of 334 mbar.

Since the workshop foreman himself didn't know what was causing this value, he called Skoda, but they were also unable to help him.
*loud laughter* I'm not at all surprised. What could Skoda possibly tell such a person? 'Sorry, you're not capable enough...' Even if they told him that, it's only logical that he told you he couldn't be helped.


In other words, your idea of going to a different workshop is a very good one! Hopefully, you'll find a more competent master mechanic there!

Regards,
Private.

Hello!

I suspect there might be an issue with the fuel pressure system or/and the mass airflow sensor (MAF).

If there's a leak somewhere in the pipe connections, the intake air will whistle at a certain pressure, leading to a loss of power. I had a similar case with my car (ARL engine) - in my case, there was a crack that only appeared under a certain load and RPM, allowing air to escape, which immediately put the engine into limp mode.

It can be difficult to identify a faulty mass airflow sensor (MAF). These devices tend to malfunction or completely fail after around 80,000 km. Therefore, try swapping the MAF sensor with one from a vehicle that is known to be working correctly (MAF sensors are compatible with various diesel engines). If this resolves your problem, then the MAF sensor was the issue. You can then either replace the MAF sensor or try cleaning it, which helps in approximately 75% of cases for a certain period.

Best regards, Sindbad.

The LLM was switched immediately, but that didn't change anything.
It's probably unlikely that a new Mass Air Flow sensor, which was already defective, was installed in my car.

Can anyone recommend a workshop in the northern part of Germany (Mecklenburg-Vorpommern, Hamburg, Lübeck) that has a good reputation for dealing with TDI engine problems and their solutions?

What measurement values should be recorded during a test drive?

If you want things done, you better do them yourself.

Seat also wanted to sell us a new Duesen with NHG (presumably a type of certification) for EU R480 compliance.

While logging, I noticed that the LMM was experiencing some fluctuations.

Cost: 1 hour of casual conversation and a bit of laptop battery.

I wouldn't put any money on "is a new LLM included" unless I've seen the actual values.

m;

Saint wrote:

Bei Geschwindigkeiten über 100 km/h fehlt dem Motor die Kraft im 4./5. Okay. In 4th gear, the engine starts to feel quite strained from 3400 RPM (approximately 140 km/h), and in 5th gear, the power output reaches its limit on a straight road at around 3500 RPM (approximately 180 km/h). The fuel consumption seems to be too high even at speeds of 100 km/h (approximately 0.5 liters per 100 km). The workshop foreman also noticed the lack of power during the test drive.

I also have a Fabia (Combi) with the same engine. Mine also only reaches the stated maximum speed on the speedometer (a maximum of 190/195 km/h under ideal conditions), which is actually too low (indicating speedometer error). The forum at www.skodacommunity.de also has useful information on this topic.

Stop your timer.

130-160 km/h in 4th gear (my estimate: 8-11 seconds, depending on the road).
160-180 km/h in 5th gear (my experience: 9-11 seconds depending on the road).
(20 km before, full throttle, speedometer reading - the needle should be in the middle of the indicator when stopping).

and perform the Ulf's pull test at 2000-4000 RPM in 3rd gear (with full throttle at 1200 RPM).

Also, test your current fuel consumption at 3000 RPM in 5th gear under full load, starting from 2500 RPM – it should be between 11 and 13 liters.