Regaining boost after re-pressing gas pedal

Hello everyone,
I have mistery problem with my polo 9n3 (1.4 TDI PD, 59kW, 2007).

When accelerating hard the car will "chocke", that is:

- rpm won't go above 2500
- heavy black smoke will go from exhaust
- readings from MAF will go down (read via computer)
- engine eventually will make banging noise

Here is the strangest part:

To fix this when driving, I need to release gas pedal and press it again. Then the car will regain it's power and fix itself!

When "fixed" (after releasing the pedal and pressing it again) the car will:
- drive smooth
- drive with 100% power (just like before this problem)

Here is what's been done to fix this problem:

- fault codes read - 0 fault codes
- replaced EGR valve (old was worn) but no effect on the problem
- replaced MAF sensor - no effect
- replaced MAP sensor - no effect
- replaced n75 valve - no effect
- checked brake assist - brakes good
- checked turbocharger actuator via VCD test - work smoothly
- rechecked turbocharger actuator manually via syringe - works smoothly

Additionaly:

- When accelerating gently, the car might not chocke and drive smooth (but not everytime).

I've made dynamic logs of group 003 in VCDS which i've enclosed below:



Can anyone help and suggest what's the next thing to check? Please help.

- engine eventually will make banging noise
Just want to illicit a bit more detail. Need you to elaborate on this please, this one item would be my main worry tbh.
Someone smarter than me will take over now

When my engine is cold if stab the throttle it will lose power, blow a belch of black smoke and start to chug. If I let off and then back on the throttle she runs full power again.
My actuator arm was too short.

STDOUBT said:

- engine eventually will make banging noise
Just want to illicit a bit more detail. Need you to elaborate on this please, this one item would be my main worry tbh.
Someone smarter than me will take over now

Click to expand...

Engine makes noise that slowly changes and starts to sound like old mercedes W123.
It's hard to describe but this is terrible sound that makes you stop reving immediately because it makes you think that the engine will break down in a momment.

Hmmm.... You'll want to track that down, maybe have a look at the internals.