24V6BDW

Every time I drive e.g. 10min downhill with throttle closed, when I accelerate there is a huge white/bluish and very thick smoke behind. The smoke is so thick, I'm literally embarrassed on these events

At first, I was thinking it's a valve stem seals (having in mind 300K km mileage) but I was lazy for entire year to check a cold start exhaust condition.

A few days ago, I left it over night and recorded cold engine start and surprise, surprise, there was not a single trace of smoke!

There is no smoke on every other driving conditions as well, even when I drove it like I stole it.
I keep oil level on max, sometimes maybe a 1mm over the max, it's hard to pinpoint it with this oil dipstick since the tube is very narrow and dipstick pick up oil when removing it.

Obviously, looks like valve stem seals are not the issue here and I don't think it's a piston rings as well (did not inspected compression on cylinders).

Can this be something related to PCV system and if it is, can it be cleaned?

Any thoughts?

Sallad

So you are saying you HAD white smoke, now you DO NOT have any white smoke?

24V6BDW

I have smoke only downhill with throttle closed.
If I drive downhill in lover gear with throttle opened, there is no smoke, ever.
In any other driving conditions, there is no smoke as well.
In general, I can’t cruise and save some fuel driving downhill, I always have to keep the revs up, meaning have to keep the throttle opened.

kelisko

Not the PCV system. I had the exact same problem and replaced oxygen sensors, PCV valve, oil separator, changed oils, tried fuel additives, flushed the engine, tried oil additives, swapped the cats with other ones to no avail. I was thinking about tearing down the engine and replacing the valve stem seals as next step but I ditched the car for some other reason before I could.