kbod

I have a 2014 C250 sport previously from the 30k no oil change thread and the p0016 CEL thread, (https://mbworld.org/forums/c-class-w...ml#post8219602) (https://mbworld.org/forums/c-class-w...ml#post8167567) The good news is the valve stem seal job is Complete, and I was able to have the p0016 CEL done at the Mercedes dealer as the car received 2 new camshaft sprockets. HUGE thanks to @azblk For all the great advice. The car runs great, revs great, and no check engine light whatsoever. but my oil smoking issue is still there! Its VASTLY better now, the car is actually usable and passed smog (surprisingly). but sometimes without warning the car will just start burning oil like crazy. only when the cars oil is not fully up to temperature although, once I drive the car for 20 mins for the rest of the day it does not smoke at all. 0 smoke. But in the initial drive from cold the car will randomly smoke at times. enough to make a minor scene at a stop light that looks really embarrassing and I also noticed that when the car is smoking my idle will drop and the car will stutter and the engine runs a little shaky and vibrates a lot. There seems to be no pattern with when the car smokes only that its for a brief amount of time (under 10 seconds but enough to make a big big cloud) and its only when the oil isn't completely hot. Given this I am wondering what can possibly be wrong with the car. PCV valve?, The oil fitting on the turbo the m271 are known to break? the air pump? maybe the turbo oil seals are gone? Im not sure, but I know the car is running well and makes full power. any advice is appreciated!!

kbod

Anyone, Anything??

I thought it might be a PCV valve but the c250 does not have a pcv valve... the m271 is confusing, Maybe its a clogged crankcase ventilation system component leading to oil being forced into being burnt which is obvious at idle but when under load is unnoticable since the engine is spinning faster... I would think its the turbo but the car does not smoke under boost. any help is greatly appreciated!!

mercjames

Considering the engine didn't have an oil change for 30k miles at one point, I would think several things would be worn, including piston rings. But, since you say it happens when it's cold, the only thing I've heard of causing that on this motor is the turbo oil feed line banjo bolt. There is an updated part with a built in check valve in the bolt that will stop you from burning oil from the turbo at startup. It's very easy to change. The bolt is on the top of the turbo with an oil line connected to it.

chassis

Burning oil means oil is getting into the combustion chamber. It can arrive there via crankcase, intake or valve guides.

You mentioned the valve guides were done - could the work have been done improperly?

Do you have good compression on all cylinders?

Pull the plugs and inspect them carefully. Do they all look identically the same? Do they look different from one another?

kbod

Yes all the cylinders make great compression and the car has plenty of power. The odd thing is the car does not smoke right when you start it up it starts smoking 1 minute or 2 after a cold start and smokes randomly on idle and when it does smoke the idle drops and gets a little jittery, but once the engine is fully up to temperature it does not smoke at all until the next day.

​​​@mercjames as he mentioned I will order the replacement bolt and washers but I don't think that will fix this issue as it smokes a lot and my symptoms don't line up with those who have the bolt issues. There are 0 check engine lights on the car also.

Ill also report back on what the spark plugs look like

NZ-Merc

Defiantly sounds to me the turbo seals are worn which lets oil in to the exhaust housing when sitting, when starting no smoke until when the exhaust housing of the turbo is hot enough it burns off as thick white smoke.
Yes this can be intermittent and common problem with any higher milage turbo engine and only fix is remove the turbo for O/H.

Dave.

ItalianJoe1

Does your car have the updated oil feed line check valve bolt on the turbo? There was a bulletin for startup smoking on the late M271 cars for that, to install the updated bolt and washers.

kbod

I think my plan is to find a used preferably low mileage turbocharger and replace mine with it, and in the process of the install I will put the updated washer and bolt!