Nissan Almera 2.0D: Jerking, Stuttering, or Hesitation?

Hello everyone,

I, or a friend of mine, am having a problem and don't know what to do anymore. (Of course, otherwise I wouldn't be posting ).
He drives a Nissan Almera 2.0D with a naturally aspirated diesel engine, producing approximately 75 horsepower, and it has around 200,000 kilometers on the odometer.
"For some time now, there has been a noticeable shaking or vibration between 1,000 and 2,000 RPM, which seems to be gradually getting worse."
Furthermore, I've observed that each time I turn off the gas, a significant cloud of smoke comes out the back (I personally can't quite explain this; could the pump be injecting fuel for too long?!).
Fuel consumption is slightly increased, but the performance is normal.

We have replaced the air and fuel filters (yes, new spelling ). There was little to no improvement!
There are no errors stored in the engine control unit. The pump (not Bosch, but Zentex) was read out, and it apparently showed some errors, but the Nissan workshop couldn't interpret them and sent us home... ATU/Bosch cannot read out the pump .

AGR has also been temporarily shut down for testing purposes, but without any positive results.

I personally suspect the pump.

Does anyone know this engine or have experienced a similar problem with other naturally aspirated engines? Do you have any other suggestions for what the issue might be besides the pump?

Thank you to everyone who takes the time to read my post!


Matze.