Audi A4 B5 1.9 TDI AJM - No Boost after Warming Up: Turbine Issue, N75 Valve or Other Cause?

Problem with the turbine: after warming up, it stops working, after pressing the pedal at about 2000 rpm there is no increase in torque. Engine after set renovation, turbine disassembled and cleaned (steering wheels and rotor), I did not notice any play in the bearings - flooded with oil before starting. Of course, a new air filter. Is it just the N75 or something else?

Hello. The problem is only on a hot engine? From the angle to be sure that the turbine or valve were taken in real time? The vacuum lines are surely well connected? The flow is operational?

Readout of block 11 parameters in real time and it will be seen if N75 is being controlled and what is happening with pressure.

The problem manifests itself when driving on the ring road with speed => 100 km / h. Until it warms up, it is dynamic, then accelerates poorly. Question to the Sulof1601 column: about which flows. it comes (there are 2, one behind the air filter, the other behind the intercooler). The answer shows that, however, I should connect to the computer.

I do not know if I understood the question correctly, you only have one flow meter behind the air filter and behind the intercooler you have an air temperature sensor and a boost sensor. I meant to check the thin wires to the turbine from the N75 valve and whether the pear pulls the cable to the end after starting the car. yet the computer or the flow indications are not distorted and what is happening with the turbine is reloading or not recharging. How did you clean the turbine, did you change the position of the pear strand? The geometry is surely correctly folded, everything worked lightly? only some mistake can happen to anyone.

Thanks for the clarification. The turbine was assembled rather well, the steering wheel worked smoothly, the impeller turned without resistance. I marked the position of the tie rod as it was before disassembly. Yesterday I noticed the following phenomenon: under the aforementioned circumstances (hot engine, speed> 100 km / h), the turbine stops working during acceleration (cuts off at about 2500 rpm). If the engine is interrupted for a moment, the turbine pulls again.
To clarify your advice - is it the electrical connection of the N75 valve or the vacuum hose?

The controller sees a boost or an overcharge and for this reason it disconnects the turbine.
Without a computer connected you will be looking for a month and you don't know if you will find it. Now it is not known whether the problem is due to overcharging or undercharging.
There may be a problem in the vacuum, a coarse hole, a damaged N75, a jammed geometry.
In my opinion, this is not the fault of the flow meter.

But this can be seen after a dozen or so minutes of driving with the computer on your lap. And this topic has already been four days ...

Added after 1 [minutes]:

You don't have a tester? Sorry, when there are no plates at home, then for dinner to a restaurant ...

I warmly welcome

I will try to briefly .. when buying the car in 2015, the seller informed me that there are vacuum hoses to be replaced because the turbo shutdown error occurs occasionally, I said "ok", that "no problem - I will replace it at my free time .."
Some time has passed, the error once was once no but it did not bother so much .. One day I decided to replace it. In fact, practically everyone was split at the valve nozzles and there was no doubt that they were to be replaced ..

After replacing all hoses - art after art, of course (not to be mistaken) exactly the same problem appeared at 2500-3000 rpm. and speeds of about 100 km / h turned off the turbo. "Reset" helped with the ignition for a while ..
The turbine blades and the whole mechanism were functional, the coo was fine, but still on the VAG error - an anomaly in the boost pressure system ...
I read on some forum information about checking the resistance of all sensors, i.e. N18, N75, N239. They were all in the range of 14-20 Ohm, which indicated that they did not have a short circuit, etc., then I measured the voltages on the plugs - result: first pin - 12V, second pin - 3V on all.
I totally went crazy .. I deleted errors and did tests over and over again ... I didn't know what to check anymore .. Because I changed everything .. Flow, mapsensor and sensors - no effect ..

After two weeks of struggle, I ruled out all possible mechanical and electronic faults and finally started checking the correct connection of the vacuum hoses ... and shot at "10".
It turned out that some of my "predecessors" caused that the hose from the outlet "out" of the N75 valve instead of in the turbine bulb was in the lower connector of the N239 valve !!.
After swapping these two hoses, the engine went crazy and rocked to 4500 rpm without turning off the turbo ..

I recommend that you find "Schematic diagram of the vacuum system 1.9 AJM" and compare it with your engine .. It helped me, I hope that this post will help someone

best regards
Michael