T4 Turbo Problems After Engine Swap: ACV to AJT

I bought a Caravelle from the year 1997 with an ACV engine some time ago, and it has a damaged engine.
It has now been replaced with an AJT engine manufactured in 1999.
The ESP (Engine Control Unit) and the fuel injectors on the AJT have been swapped. Only the flywheel is from the AJT (it's slightly lighter but practically new). I believe the rest of the components are the same between these engines, and hopefully, the turbo as well.
Now the ESP is perfectly calibrated.
However, the real driving pleasure hasn't quite emerged yet.
The turbo simply refuses to engage.
There are no errors in the error memory.
All the hoses are connected.
What I noticed during the first engine run after the long winter break was a rhythmic hissing or whistling sound (at idle).
Unfortunately, I was unable to identify it.
That's gone now.
In addition, I installed an aluminum plate at the inlet of the EGR valve.
It might potentially leak because I only used one seal.
But it's not hissing anymore.
Since I bought the T4 with engine damage/non-running condition, there could unfortunately be many issues.
After doing some research on my own, it's worth mentioning that the engine had been sitting unused for a while.
But after researching the TDI problem site, I don't think a faulty pressure sensor is the issue.
The bus accelerates smoothly and consistently from start to finish, but without any sudden bursts of power.
It doesn't make any noise from the back either.
Maximum speed: approximately 135 km/h.

Best regards, Klaus.

Since you mentioned that the error memory is empty, it seems like you have the ability to perform diagnostics.

I can therefore highly recommend the article "Troubleshooting with VAG-COM: A Systematic Approach," which you can find on this page under "Technical Articles." This should help you narrow down the problem relatively quickly.

Regards,
Sure.

PS: It seems very strange that there's a completely missing turbocharger without any error messages being logged.

Luckily, I know someone at Volkswagen who can operate the diagnostic tool.
And it only costs the price of one case of beer to read it 100 times.
As I mentioned, my acquaintance precisely adjusted the fuel injection timing of the ESP yesterday.
However, no fault could be detected in the control unit.
I have to go back anyway, and I can reattach it then.

Now an error has occurred.
Intake manifold pressure.
Rule difference.
The turbo is okay.
However, the solenoid valve is not clicking when activated by the diagnostic device.
The guy says it should.
Unfortunately, they didn't have one available at Volkswagen for testing.
I'm going to try installing a functional prototype tomorrow.
Best regards,

Unfortunately, there's still no good news from the "Turbofront" project.
Today I installed a new electric switching valve and mass airflow sensor, and they are both working perfectly.
But unfortunately, there's been no improvement.
There was some water on the metal plate in front of the EGR valve, which I just removed.
Is that condensation, or something worse?
I probably won't be able to proceed without reading the error codes again.
Have a great weekend!

I tinkered with something again today.
That pressure gauge caught my eye.
I compared it to a different bus.
She was feeling quite down.
So, the rod was under too much tension.
So, all the pressure has been released.
Something probably got stuck during transport.
Then I pressed it up a bit, and the turbo boost was back.

Best regards, Klaus.

Klausen wrote:

The pressure chamber... was pushed down quite a bit. Please provide the text you would like me to translate from German to English. I will then give you only the translation. Then she pushed it up a little bit, and the turbo boost was back.

There's just so much out there... that would actually be a perfect topic for a competing article focusing on common mistakes.

"Causes of errors that no ordinary mechanic would think of," or something like that...
is not meant personally .