M50B20 vanos Vacuum lines

[Mihnea"e34]

I have a problem with my engine since i got the car. On cold start it stays on normal idle, but after warm up it bounces between 1100-1600rpm.
The engine runs good and revs normaly without delay or cuts, and pulls strong.

The primary suspect is the PCV valve, because a vacuum leak will affect the whole range of rpm and make the engine run like crap, but the PCV only controls the idle.

That being said, Is there a list of all the vacuum lines on the m50b20? Or at least what size the hoses are? I want to check them all and might even pull the intake off.
Will new gaskets are requierd every time i pull the intake off?

[Billyj]

If the gasket is old you will need a new one. The ccv doesn't control idle per se

[Mihnea"e34]

But has influence over it? what does it do exactly?

[B320i]

M50B20 uses the same two breather hoses as the other M50 engines. There is no PCV valve per-se.
The valve cover is designed to prevent large amounts of oil going through the breather hoses into the intake system. I don't know if this setup has a no-return function or anything like that.

I've played around with the hoses in the past (when replacing them). They made the idle a little rougher and that was about it. Opening the oil filler at idle does the same thing. Now, if you removed the brake booster hose, the engine will run like a POS.
Part numbers for the hoses are as follows:
- Fatter PCV Hose (into intake elbow): 11151730507
- Smaller PCV Hose (near ICV): 11151726828

Can't link you the Bimmerforums thread about the Vacuum Diagram - as the images were hosted on Photobucket, and we all know what happened there! >

To answer your question on the intake manifold, yes, the gaskets must be replaced every time.

[Billyj]

PCV stands for pressurized crankcase ventilation. Essentially in it's simplest form it is simply an open vent, usually on the valve cover. Next best would be a breather vent with a filter do you don't intake dirt.
Most commonly it is a tube with a one way check valve in the middle. One end of the tube is connected to the crankcase above oil level and generally baffled to prevent excessive oil consumption and oil in the crank case is to some degree vaporized. The other end is connected to the intake where the desired level of vacuum is commonly seen.
With this system in effect, the blowby from combustion and subsequent crankcase positive pressure is relieved by the vacuum created by the lower pressure air being drawn/pumped through the intake. Thus all combustion gasses that are already accounted for either make it out the tailpipe or are reintroduced to the combustion process.
On newer BMW engines this is vacuum level is metered by a diaphragm. A lot of newer BMW engines also use low tensioner rings on the Pistons that will experience flutter if not exposed to low level vacuum on the crankcase side. These CCV or crank case ventilation as apposed to PCV pressurized crankcase ventilation, also feature oil return lines that help condenser and return oil to the sump while still burning off moisture.

That was a lot of information hope it made sense lol
Don't treat that as law, it's just my working knowledge on the subject

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But has influence over it? what does it do exactly?

IAC generally controls idle on computerized engines. It simply stands for idle air controller. It is a soleniod that moves a valve and allows air to bypass the throttle plate

[ross1]

Positive crankcase ventilation. The first form of emissions control. It replaced road draft tubes which ventilated crankcase blowby to the atmosphere. Drawing it in (crudely metered, hence the valve) with the intake charge eliminated those emissions.
It also serves to keep oil from being contaminated as quickly by those gasses. Applying negative CC pressure can improve power but requires the CC be very well sealed.

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