1.4 tsi smoking and high oil consumption

[Bryden02]

Hi Guys

I have a workshop specializing in BMW and MINI. About 8 months back a customer of ours brought in his scirrocco 1.4 tsi for a misfire and rough idle.
carried out a compression test and it to be low on two cylinder.Found pistons had failed. Did a complete engine rebuild taking no shortcuts (new pistons, oil pump, camshaft adjuster, timing chain kit etc,etc) Car has being running well for six months with no performance or idling issues, now but has slowly started to consume oil and has oil puff from exhaust on cold start.mimi
Did a few checks and found the charge lines and intake soiled with oil. So we had the turbo reconditioned to take worn turbo seals out of the equation. Removed all charge lines and inlet to clean, reassembled and tested. Rechecked and found slight oil in charge lines and inlet again. Found car still smokes from exhaust on cold start.
Not sure what the problem could be.
Are pcv common problems on these engines?
Any help will be greatly appreciated.

[blower]

Causes of high oil consumption:

-Turbo seals leaking
-Valve stem seals leaking
-High blow-by (piston ring failure / piston failure)
-PCV issues

On this engine PCV failure is uncommon. The system used is a dual valve - a small one with a natural restrictor for when the engine is idling (under vacuum), and a larger valve for under boost. Due to the design it is unlikely to cause increased oil consumption, particularly in the intake/charge lines if it failed.

Valve stem seals or valve guide wear would cause increased oil consumption and I have seen a few cases with valve stem seals and a case where the guide needed changing. However it wouldn't cause excessive oiling of the charge lines.

If you have removed the turbo out of the equation, with excessive oil on the intake I am more inclined to think an issue with the pistons/rings.

Perform another compression test if you haven't done so already. you should be getting 150-200psi on each cylinder, usual for a low wear engine is around 170psi.

[risingson]

Asking a novice question here, but how are compression tests done? Is there an opening on each cylinder to connect a piece of equipment to?

Sent from my SM-G928F using Tapatalk

[blower]

Asking a novice question here, but how are compression tests done? Is there an opening on each cylinder to connect a piece of equipment to?

Sent from my SM-G928F using Tapatalk

Compression tests are always done via the spark plug holes. You remove all plugs, disconnect/disable the fuel pump, cycle the engine a few times to eject any fuel, then screw in a pressure gauge to 1st spark plug hole and cycle the engine. The gauge reads maximum pressure achieved, and you do this for each cylinder (spark plug)