Something I wrote 9 years ago now.
Tensioner revisions. Revision 1 engines built fom 17 May 2010
Revision 2 engines built from December 2011.
Revidion 3 engines built from 01 May 2012.
What happens.I'll keep this short.
. The tensioner on the camshaft chain tensions by oil pressure.
. When the car has no or low oil pressure (car stood overnight or during work day) the tensioner falls back on its ratchet to keep tension on the timing chain.
. Its the ratchet that fails in the tensioner, therefore releasing tension on the chain.
. When you go to start the car, the chain is slack as the ratchet has failed.
. The chain moves on the sprockets and moves a couple of teeth before oil pressure builds and tensions the chain once again, but sadly in the wrong location as its moved teeth on one or more of the sprockets.
. Due to the timing been incorrect the ECU tries to keep the car running by changing the camshaft timing.
. As it cannot adjust enough the car either runs poorly or does not start at all.
. Due to the timing been incorrect. Engine Pistons meet cylinder head valves etc.
. Result=New engine needed or at least a rebuilt one.
New 06K 109 467 K and Old 06H 109 467 AB 
The ratchet of the old version
Parts needed to change just the tensioner ~£300 to do at a specialist.
Parts if changing the chain and guides (if going to this length i would change sprockets but thats me(VW don't do this)) ~£1200 to do the job by a VW dealer (note: cover not shown but imho should be changed as well)
