AJM boost pressure

Hello.

I have a Bora 1.9 TDI with the AJM engine and I'm experiencing the following problem:

"It often happens that the car goes into emergency mode while driving. When this happens, the engine speed only increases as far as it did when it switched to emergency mode. You have to turn off the ignition and restart the car, and then it will run normally again."

The fault code 17965-Charge pressure control, control limit exceeded, is stored in the fault memory.
P1557 - 35-10 - Interrupted, placed down.

When logging the boost pressure, I'm seeing a maximum of 2590 mbar. With a different AJM (engine), it's 2400 mbar. The boost pressure control valve is at 94%, or with other working AJMs, it's at 75%.

"First, I swapped the AGR valve and the boost pressure valve - no change."

Then I replaced the boost pressure sensor, but there was no change.

I also extended the rod on the boost pressure sensor, which further reduces the boost pressure. According to the measuring device, the boost pressure remained relatively constant, but I experienced a misfire at around 2000 RPM during acceleration.

My suspicion is that the guide vanes in the turbo are no longer directing the airflow as they should, even though the lever can be turned easily from stop to stop.

I might try tightening the adjustment screw on the turbo a bit further; maybe it will make a difference.

Perhaps someone else has encountered a similar problem and can help me.

Thank you very much.

Christian

Quote:

Furthermore, I extended the rod on the boost pressure sensor so that the boost pressure is regulated even further down.

That's not entirely correct.

The charging pressure is adjusted to the same value using rods of different lengths.

Exactly because it's a regulation. The length of the rod is just a parameter that determines how "aggressive" the regulation is. If the rod is too short, it becomes so aggressive that it causes overshoots, which the software then recognizes as errors.

However, if the rod length exceeds a certain limit, either upwards or downwards, the stroke of the cylinder or the valve's adjustment capabilities are no longer sufficient.

m;

Regarding the fun, there are complete lectures on control engineering.

chli1976 wrote:

In the fault memory, the error code 17965 indicates that the boost pressure control has exceeded the regulation limit. When logging the boost pressure, I'm seeing a maximum of 2590 mbar. With a different AJM (engine), it's 2400 mbar. The boost pressure control valve is at 94%, or with other working AJMs, it's at 75%. Werde dem nächst noch die Einstellschraube am Turbo noch weider hineindrehen vielleicht bring es etwas.

I wouldn't adjust that, because it's very precisely calibrated from the factory.
It's a good idea to take a closer look at the pneumatic hoses.

Quote:

Meine Vermutung ist das die Leitschaufeln im Turbo nicht mehr den Weg machen den sie sollen, obwohl man den Hebel von Anschlag zu Anschlag leicht drehen kann.

It shouldn't be easy to depress, but rather require a significant force from the pressure capsule. If that spring, for example, is broken, your symptoms would make perfect sense.

I completely agree with Ulf. However, before doing anything else, try testing the vacuum part after the valve again using a large syringe (perhaps from a pharmacy).
If you press the VTG rod with your hand, you should feel a noticeable resistance, as Ulf mentioned. If you don't feel that resistance anymore, you'll know where to start looking.
How much have you twisted the VTG rod? Are you using a live data display (LDA) or reading values with a VAG Com?

Hello.

Thank you to everyone who responded.

When I said "leicht," I meant with the pressure canister detached, so only the adjustment lever on the guide vanes.

chli1976 wrote:

By "LIGHT", I meant with the pressure canister detached, so just the adjustment lever for the guide vanes

.
Aha...

Is the normal adjustment range (approximately 1 cm) available?

Is the can (as far as can be felt -> referring to the spring force and seal) intact?

Hello.

Thank you to everyone who has already responded.



After many unsuccessful attempts, I replaced the turbo, and now everything is working perfectly again.

Hello.

Thank you to everyone who has already responded.



After many unsuccessful attempts, I replaced the turbo, and now everything is working perfectly again.

Hello Christian,

I'm glad to hear that your AJM is working properly again!

Unfortunately, I haven't gotten that far yet.

Did you perhaps create any VAG-COM logs after the installation?
It would be interesting to see how a completely intact AJM engine regulates boost pressure.

Best regards.
herwig

No, I haven't, but I will do it when I have the chance.