T4 2.5 TDI: Fuel injection timing fluctuates

Hello, I used VAG-COM to read the fuel injection start timing, and it's fluctuating between 50 and approximately 65 (at idle).
Is that normal?
In the MWB 11 system, the calculated charge air pressure is 1132 mbar, but the actual measured value is only 979 mbar. The engine speed is 775 RPM.

at speeds of 1163, 1162, and 979 (no typos).


At speeds of 2300 -- 1400 and 1000.

Mileage: 194,000 km. Blue smoke after starting, but it disappears after about 2 km.

Oil consumption: approximately 0.5 liters per 2500 km; no water consumption.


Can someone help me?

Thank you, Wagner H.

Hi there,

Hello, I read the fuel injection start using VAG-Com, and it fluctuates between 50 and approximately 65 (at idle).
Ist das normal?
Minor fluctuations are normal. But this seems a bit excessive to me. Is the timing belt tension still correct?
-> http://www.t4-wiki.de/wiki/Einspritzpumpe (2.2 and 2.4)


In the MWB 11 system, the calculated charge air pressure is 1132 mbar, but the actual measured value is only 979 mbar. The engine speed is 775 RPM.

at speeds of 1163, 1162, and 979 (no typos).

At speeds of 2300 -- 1400 and 1000 .
The values (difference) don't look very good and suggest a problem with the boost pressure control system and/or the turbocharger itself.
It's perfectly normal for the turbocharger pressure to be low because the engine is running without a load.

Are there any error messages?



Mileage: 194,000 km. Blue smoke after starting, but it disappears after about 2 km.

Ölverbrauch ca 0.5 ltr 2500 km, kein Wasserverbrauch.
For an ACV (presumably referring to a specific type of engine or component), that's quite a lot of oil loss. A well-maintained ACV typically only needs topping up between oil changes.
The oil leak and the blue smoke could indicate a problem with the turbocharger. You can find information on troubleshooting, including a basic mechanical inspection, in this link.

Hello, I don't have any error entries. My bus was in the workshop today; the start of boost was checked and readjusted (not yet read out with VAG-COM).

Okay, now about the turbocharger – mine has a slight amount of vertical play (up and down). It also has some play (about 5mm) from the compressor side to the exhaust side. However, it's not sticking or difficult to turn.

Is that normal?

Thank you, Helmut.

Hi there,

Now, regarding the turbocharger -- my turbocharger has a slight (minimal) play up and down. And there's also some play (approximately 5mm) from the compressor side to the exhaust side. However, it doesn't surge or feel difficult to turn.

Ist das normal?
The turbocharger is allowed to have some radial play (up and down movement, a few tenths of a millimeter), but it should not have any axial play.
And your turbo actually has 5mm of play? That's not good...

It's possible there are fewer than 5, but definitely 2-3 mm. However, there is no contact between the casing and the rotating part, whether on the exhaust or pressure side (always rotated from the pressure side).


If the turbocharger is faulty, how do I perform a test drive using VAG-Com? Which measuring blocks (OBD-II parameters) are needed?

best regards, Helmut

Hello,

- The axial play of the shaft is only slightly more than 1/10 mm and is also difficult to detect because the internal contact surfaces are lubricated with oil, which prevents a "hard" stop from being felt.

- The actual radial play is on a similar scale.

However, the shaft runs in a floating radial bearing sleeve, and when testing it unilaterally, usually by wobbling the end of the shaft near the compressor, the shaft tilts, and the clearance appears to be "excessive" for proper support.

The difference between genuine radial play and a combination of radial play and tilting can be recognized as follows:

Simultaneously, hold both the compressor-side shaft end and the turbine-side shaft end between your index finger and thumb. Press both shaft ends upwards/downwards once in a synchronized motion, and then press one shaft end upwards while pressing the other shaft end downwards.

As long as there are no visible signs of wear on the compressor housing, the bearings are in good condition.

"And I don't think you can feel a clearance of 2-3mm. I'm always surprised how small clearances that are felt can seem large. 0.1mm of valve lash is nothing in mm, but it's definitely noticeable, and it feels like the rocker arm is moving significantly."

Regards,


Andreas

Hello,

- The axial play of the shaft is only slightly more than 1/10 mm and is also difficult to detect because the internal contact surfaces are lubricated with oil, which prevents a "hard" stop from being felt.

- The actual radial play is on a similar scale.

However, the shaft runs in a floating radial bearing sleeve, and when testing it unilaterally, usually by wobbling the end of the shaft near the compressor, the shaft tilts, and the clearance appears to be "excessive" for proper support.

The difference between genuine radial play and a combination of radial play and tilting can be observed as follows:

Hold the shaft end on the compressor side and the shaft end on the turbine side simultaneously between your index finger and thumb. Press both shaft ends upwards or downwards at the same time, and then press one shaft end upwards while pressing the other shaft end downwards.

As long as there are no visible signs of wear on the compressor housing, the bearings are in good condition.

And I don't think you can feel a clearance of 2-3mm. I'm always surprised how small clearances that are felt can seem large. 0.1mm of valve lash is nothing in mm, but it's definitely noticeable, and it feels like the rocker arm is moving significantly.

Regards,


Andreas

Hello. I need to re-examine everything again on Saturday. It seems like the wave might be shifting (axially). Let's wait until Saturday.

How can I perform a measurement run with VAG-COM? Which control modules (OBDII codes) and what data should be displayed during the process?
Thank you, Helmut.