Golf Mk6 - CBAB Engine - Engine knocking - Possible Boost Issue ...

[chopper_harris]

Folks

I have a curious issue after replacing the turbo actuator on a 2009 2.0 GT TDi with CBAB engine.

From standstill, if I pull away in first gear with normal acceleration, when I reach 1,800 rpm I get a harsh knocking sound from the engine and it will not accelerate past 1800 rpm.

If I back off the accelerator and then apply normal foot pressure again, the car will accelerate smoothly to 2,000 rpm, and then pulls away like a scalded cat.
Once on the move, the kick in the pants is repeatable when accelerating though the 2,000 rpm point.

It is as if the boost is cutting out/in at 2,000 rpm ?

The turbo actuator was dialed in to exactly 0.76v on full deflection with VCDS block 120, and I have confirmed that is repeatable on VCDS with a Mityvac on the actuator vacuum port.

There is good vac supply from the pump and no leaks detected with the Mityvac on either side of the N75 valve.

There are no codes on a VCDS full scan.

What am I missing ? Why is the 2,000 rpm point significant ?

Any guidance would be greatly appreciated.

Thanks

[chopper_harris]

Not a single comment or suggestion - has no one seen this issue before ?

[Crasher]

Sorry I missed this first time around but no it doesn’t ring any bells; presumably before you fitted the actuator the problem wasn’t there? Genuine actuator and any new fault codes?