VW T5 AXE - Reduced Turbocharger Boost

Hello, Diesel Truckers,

I have a VW T5 Bus, manufactured in 2004, with a 2.5 TDI AXE engine and 218,000 km.

Here are some things I have already done:

Turbocharger, camshaft, hydraulic lifters, automatic transmission, half-shafts, PDE wiring harness.

I bought the car used. During the purchase, he had the problem that it would jerk very strongly at approximately 1800 RPM. However, it had full power (174 horsepower). VW believed that it was the automatic transmission.

This was repaired, but the problem remained.
Subsequently, the camshaft and hydraulic lifters were replaced (they were actually very worn), along with the PDE seals and wiring harness.

Now it's running, but it still has a slight vibration and lacks power.

Subsequently, VW stated that the turbocharger was not functioning correctly, and as a result, the turbocharger was replaced. Unfortunately, no improvement.

I've just purchased a VCDS and have read the following values:

At medium power, the target boost pressure increases, but the actual boost pressure does not (Tempomat, highway, 130 km/h, beginning of a slope). Then the target/actual value differs by 0.5 bar, which causes it to enter the emergency program.

It seems that MSG did not even attempt to increase the boost pressure, as the curve for the control is relatively constant.

However, if you give it full throttle, you can see that the actual boost pressure follows the target pressure relatively well, with some overshoot.

I've now managed to seal the AGR, and there's a slight improvement.
LMM Value: CURRENT 420, TARGET 280 in LL

What seems strange to me is the 4th value in a measurement block (I need to find the number first), which has the value -3.4° (below it is "IDLE Stabilization").

The engine starts up perfectly, but has no power, and according to my assessment, the fuel consumption is much too high.

What else can be done here? I'm pretty much at the end of my rope.

Hi

Quote:

At medium power, the target boost pressure increases, but the actual boost pressure does not keep up (Tempomat highway, 130 km/h, starting incline). If the target/actual pressure difference is 0.5 bar, it then switches to the emergency program. It seems that MSG did not even attempt to increase the boost pressure, as the curve for the control signal is relatively constant.

If there is a significant difference between the target and actual boost pressure values, and the engine control unit (ECU) does NOT adjust the VTG (Variable Timing Control) control (measurement block 11 in the ECU) in the short term, then it is possible that you have a faulty tuning in the ECU.

Please log the data blocks 1, 8, and 11 from the engine control unit during a full-throttle acceleration at 1500-4000 rpm, and then again for a few seconds when your engine control unit switches to limp mode due to low throttle.
Furthermore, we also offer {SERVICE_TYPE}. The designations for the data blocks in your engine control unit seem strange, possibly the engine control unit was swapped with a different type, therefore please add an auto-scan.

Best regards, Rainer

Hello, here is the log entry.

From Marker 100-130 full throttle


Then, at Marker 270, the pressure was reduced.

Autoscan is next.

@English names: it might be because I accidentally installed the English version.

AGR: is closed with a metal lid.

According to the previous owner, no engine tuning has been performed, and the car was always serviced exclusively at the dealership.


Okay, hier ist die Übersetzung:

Now, let's add "with Autoscan."

Hi,

Quote:

AGR: is closed with a metal lid.

leads directly to emergency mode, remove.

If the turbocharger is new and not faulty, and the boost pressure sometimes doesn't build up, then it can only be due to a lack of vacuum to operate the VTG (Variable Turbine Geometry) or a malfunction of the VTG itself.
Check if the vacuum system has the necessary vacuum pressure and if there are any leaks in the vacuum hoses or other fittings between them sparking.

What's also problematic: The boost pressure can also be too high (2601 mbar is the maximum value that can be displayed via diagnostics, but in reality it could be higher), which means either the VTG or the solenoid valve for the boost pressure control in the vacuum system is malfunctioning. Therefore, there is likely no lack of vacuum.

Best regards, Rainer

Hello,

I've just got the AGR working properly again, just like it should. It seems like there won't be a new "Notprogramm" after all.


But he needs 0-100 in 23s (the Mercedes G300D 25 years old from my brother needs approximately 21s, but without a turbo and with more weight).

What other metrics can be monitored to assess performance?

Thank you for the previous information and tips, and hopefully, the ultimate solution will come.

Could it be that something might be wrong with the camshaft timing, as it was recently replaced?

EDIT: The fuel injection system is back in operation, and the valve for the fuel pressure regulation has also been replaced.

Are you sure that's a new turbo? Line 388 shows it at 2601 mbar (11/3), which is the maximum that can be displayed. The dead zone goes down to 15%, so there's almost no vacuum at the VTG dose anymore. Then 1 sec later 1958 mbar.
For me, it looks like a difficult VTG. As long as no changes were made to the file.

At Marker 270, you're not even pressing the gas pedal...

Could the problem essentially be due to the camshaft being slightly misaligned?

Purely theoretically?
Or would one read that in some measurement blocks?

axpdreamer wrote:

Could the problem essentially be due to the camshaft being slightly misaligned? Purely theoretically? Or would one read that in some measurement blocks?

No, rather you would have had a engine damage due to colliding valves hitting the pistons. At the Cam Angle / Synchronization Angle , you can see if the camshaft is in the correct position relative to the crankshaft.

Best regards, Rainer

Hello everyone,

I'm still having trouble with my bus.

I've just created a few more logs.

MWB 1, 23, 24
and MWB 1, 13,14

Here are some significant differences if you look at them more closely.

I had the 5th injector repaired about six months ago, but unfortunately, I haven't had the others repaired yet. Now, I'm wondering if maybe the others are also malfunctioning.

213,000 km, and built in 2005.

Please provide information on whether I should replace the injectors or not. The problem persists: the car has little power, consumes a lot of fuel, and jerks in the lower RPM range (1000-2000) (no DPF). NW and the piston rings had to be replaced, as they were already quite worn.

Please help.

Hello,

In my experience, the actuator rods of PD elements wear out over time, which manifests as "more turning back when adjusting the PD setting."
Therefore, the difference in the idle reserve rule for PD elements when only one element is replaced is not really surprising. I suspect that only the new element was discontinued, and not the 4 older ones?
Turn off everything, and do it correctly, see the instructions in the technical article.

But it has nothing to do with the reduced boost pressure, what about the previous posts, have you found anything out or are you just swapping out PD elements for fun?

What about...?
/viewtopic.php?p=238219#238219
/viewtopic.php?p=238224#238224

Best regards, Rainer

In a good mood, I'm no longer doing anything with these cars .

NW, was was
Turbo has been renewed (for the 2nd time)


I'm really at the end of my rope.

"Undervoltage is still present, AGR is original as it should be."

All elements have been re-installed.

When the 5th injector was replaced (repair by Bosch service), it noticeably improved. Before the replacement, it seemed like the dashboard was the problem. (Very strong jerking in the partial load range at 1400-1800)

Should I create more logs?

Hello everyone,

For clarity: The problem was resolved by checking the PD elements. Injector 3 had a faulty coil.


Best regards
axp