Hissing engine

[EstonianE89]

So I've been having problems with my E89 23i lately. Symptoms are following: High L/100Km (13+ when driving in city), rough idle sometimes right after starting up,sometimes stalling right after breaking/before speed bumps after a short period from start of drive, some white smoke coming from behind, sometimes fuel smell on startup, some periodic vibrations going trough car. and now just today I noticed perioodic hissing from the front of the engine (constant hissing, but it pulses louder about 3x per second). I brought it to the official dealer in my country, they said they couldn't detect much, just that the VANOS params were off and they reset it. What could it be and how do I go about diagnosing.
Note: I have ISTA+ and most tools you would need to fix a car and looking to do it myself this time.

 

[EstonianE89]

It was -15C degrees outside, but still the smoke spread quite far.

 

[Pondy]

Welcome to the forum.
Are you sure the white smoke isn't steam, in -15 temps?

 

[EstonianE89]

I mean it could be that but it also smells gravely and it lingers for quite a bit.

 

[B21]

So what are the fault codes?

 

[flybobbie]

My 23i is very steamy around 0 degrees, had me concerned it was smoke, but doesn't smell of smoke and no coolant lost.
Around 90k miles i had too replace the cam cover, on start unstable idle, found oil in no.4 spark plug hole.
Cam cover comes with new oil separator built in if it exhaust smells of oil.

I always get strong fuel smell on start up, often looked for a fuel leak, but can't find any.

 

[EstonianE89]

@B21 There are none

 

[B21]

Sounds like a problem with the fuel circuits like a faulty exhaust cat sensor …have you checked inlets for issues…what do the short /long term fuel trims say?