BMW F01 N63 Excessive Smoking and Knocking

[Profpetrof]

Hi All,

Before I get sent to the valve stem seal thread, they were apparently already replaced, so please hear me out.

First off, I own a 2012 BMW 750i with the N63 Hot Vee motor.

Since 70,000 km I have only had bad experiences, misfiring when cold, Engine errors when tank low, and excessive oil consumption. BMW Dealers in South Africa are renowned for their sub-par service and client relations.

At just over 100,000 km we finally had the valve stem seals replaced, after a lot of fighting, ended costing ZAR 80,000.00 of which BMW covered part of it.

Now here lies the problem, the car is now 10 months older, 10,000 km later, and it is smoking excessively. This smoking is intermittent, and only happens when you leave it idling or slow town driving, and then try and accelerate. The car will detonate badly, and then expel a smoke screen of white/gray smoke.

BMW took the car, and after a month of analysis suspect one of the cylinder liners are scratched, and it will now cost ZAR 460,000.00 to replace the block. This on a car with just over 100,000 km on, in pristine condition.

My questions are, what are the chances a scratched cylinder can cause intermittent smoking (refer to photo), what are the chances this is still valve stem seals (poor workmanship), and what else can it possibly be.

If the car is started cold in the morning and I drive mainly highways it runs perfectly. No smoking, no detonation and no errors.

I am convinced that this is due to lack of proper maintenance and poor diagnostic from BMW.

I would appreciate any assistance on this matter, or opinions, technical help...