PCV open at idle?

[Ferret]

Gents,

How should the PCV plate on a V8 behave?

I'm currently chasing a rough idle on the 540, and have started the stripdown to do the intake gaskets.

However before I started the stripdown I looked at the following:

Opening the oil cap makes no change to the idle
While half-torn down, I've popped the breather tube off the PCV plate and started the car. The idling went to a really heavy thrunka-thrunka-thrunka shake and there was an unholy whistling noise coming from the pcv unit.
Putting my thumb over the pcv intake stopped the whistling and caused the car to return to a much better (if still lumpy) idle...

In the end I didnt pick up the cam sensor as the one at the dealer had exactly the same resistance, but picked up the gaskets instead...

Anyone know if the crank and cam sensors should differ resistance on the V8?

Now it seems I may need to pick up a new pcv plate as well as all the gaskets :/

Might drop the exhuast first mind to see if I've got a shot cat after all the smashing on speedbumps they get around here :/

[MBXB]

Ferret,

This is a well known problem and been well covered by this board's gurus.
All it takes is one buggered up gasket, rubber hose or cracked clamp point to mess up your idle and make you crazy.

Check out this thread in the archives:

http://www.bimmernut.com/forum/showthread.php?t=19452

Pics of intake manifold removal:

http://rides.webshots.com/album/547573582fsDOsR?vhost=rides

Before you start removing cats and exhaust manifolds, I would make sure that the intake system doesn't have a leak; and there are many places it can. I replaced all rubber that had anything to do with the intake manifold, the Front and Rear intake gaskets, the PCV plate itself, and the O-rings.

Also, while I had the intake manifold off the car, I had the injectors refurbed and calibrated. They looked like crap. (See the pics) They're right there in hand, so you may as well check them out.

I'll look around for that parts list if I still have it. (The bolts BMW uses on the front and rear intake plates are crap. Replace them with real ones.)

Happy Ferreting!

[Paul in NZ]

could the exhaust( you have a hole in your exhaust right??) be the culprit...maybe for peace of mind get a muffler bandage just to rule that out for now??

[Ferret]

could the exhaust( you have a hole in your exhaust right??) be the culprit...maybe for peace of mind get a muffler bandage just to rule that out for now??

The hole isnt actually particularly large tbh, it's after the cats and centre silencer/muffler - basically in a position where it shouldnt be affecting the idle.

The big clue here is that the idle doesnt change when you open the oil filler cap - the car's definitely running lean as you can see the plugs starting to get glazed...

I'm just frustrated that the dealer + parts places all close at the damn weekend - what kind of customer service is that?