bad gas milage and crankcase vent?

[pyro]

Hey,
I have a 91 525i w/ m50. I have been tring to find out why im getting bad gas milage. Im let to bieleve that it has to do with the crank case vent. because at the bottom of that hose there is alot of oil in it. this makes me think that if theres a valve in the crankcase vent that mabe its leeking. since i don't have to pass emitions again for 2 years is there anyway to eliminate it completely? can i jsut plug the hold in the intake boot and put that hose into a catch can?

im getting 11.6mpg and thats with granny driveing

im open to other ideas that can cause bad gas milage. i already tried cleaning the maf w/ brake cleaner... no change

[shogun]

You can do a quick test on the state of crankcase vacuum by removing the oil filler cap and stretch by two hands a plastic supermarket bag across the opening. The membrane should be seem pulled into the crankcase (but don't let go the bag!) if there is vacuum inside."

[tim]

The pcv valve shunts gasses and moisture from the combustion process back into the intake manifold. It is basically a spring valve, that allows flow at and above a certain positive crankcase pressure. The spring can become worn, deformed, or caked with residue. Then it may allow the loop to be open continuously, diluting the fuel air mixture with crap, and also lowering vacuum pressure.

On my 540s we have a ventilator plate pcv, which must be replaced, but on your's I think you can remove and clean it in a solvent.

I bet your intake manifold and injectors are a mess. I have used a product called Seafoam (do a search on this board as to how it is used). Use this method at you own risk (I do). I would do 8oz in the last 2 gallons of the tank, and another 8oz in the case. Do the dealio, then drive straight to the gas station like you friggen stole it (italian tune up) and fill up, and when you get home change the oil out. Put a little atf dex3+ (like a half quart) in the case when you refill and it'll help clean stuff up.

Have you gotten any codes?