idling issue

[spitfire06]

Hi guys I drive a 1999 318(e46)just this morning it started to idle a bit on the high side.I pull upto a junction it starts by dropping to about 1200rpm then slowly settles down to just under 1000rpm.Any ideas?While Im bending your ears looking to change my tyres next week they are 205 55 16 currently on Bridgestones.Im willing to pay £75-£80 per tyre anybody got any reccomendations?

[T-bagger]

Looking at the age of your 318i I'd say you have the M43TU 8 valve engine. These do suffer with a few air leaks that will cause poor idle quality. Top of the suspects list is the crankcase gas/oil seperator that sits towards the rear of the inlet manifold. These begin to leak air over time even though they look fine.
The best way to check this and for other air leaks (as split breather hoses cannot be ruled out) is to open the bonnet with the engine running and listen around the inlet manifold, particularly towards the bulkhead. You ae listening for any abnormal hissing or whistling sounds.
The seperator is a flat black plastic disc about 3" diameter by 1" thick with a rubber hose attached to it. By placing fingers on it, if it is leaking, you can ususally change the pitch of the sound. Check the hose on it also.

Hope this helps, repost if you need further advice.

[spitfire06]

Great advice mate.Popped the bonnet and just as you predicted a hissing sound.Ive located the leak to the the pipe that runs along the back at the top of the engine.Im not mechanically minded but I think it runs from the cylinder head cover and could be wrong here but I think it connects to the vacum pump.Sorry for the crap description but if someone can help me identify the name/part no that would be great.

[tommobmw316i]

Hi,

this sounds like the exact same problem that I have with my 316i SE 1999/V. Looking at Realoem.com would you be able to help me locate the location of the crankcase gas/oil seperator so I know what I am looking for.

Thanks