D2 knock, rough running after service

[clfurness]

Hello all,

I've got the D2 2011 engine in my V50 and everytime I get it back from a service a severe knock occurs when iddling and makes the car horrendous to drive.
Each time I've taken the car away and redone the learnign routine (driving full throttle up to3500rpm then letting off completely and waiting for the revs to drop to 1500rpm. Rinse and repeat until engine runs properly) and the cars been pretty much ok until the next service and the same thing happens again!

Am I right to assume there is an underlying fault here, like a tired injector or something?

Currently there's no error codes, and nothing unexpected happenign with the car other than the knock and some white smoke.

Help!