318ci Idle problems

[PhilH]

2001 318ci coupe e46.

initial running is fine and throughout the rev-range is seemingly fine also. After a while once it's warmed up (it doesn't seem to do it from cold just yet)at idle the needle shakes a little and dips down to near 0 and then brings itself back up to just under 1,000rpm.

the engine sounds like a bag of ... until you rev it. i don't think it's as misfire as it's smooth throughout the rev range. The idle problem is also intermitent. Sometimes when you dip the clutch as you break before lights etc it almost stalls but brings itself back up to under 1,000rpm.

personally suspect ICV, and a friend is to connect it into his diagnostic machine tonight; just wondered if anyone else had this issue.

phil

p.s. is the ICV easily accessible on this model or is it down below the inlet manifold? i see there are two sensors on the side of the plenum chamber.. pressumably one is throttle position sensor?

[PhilH]

thus far the scanner showed up a faulty 02 (lambda) sensor. to double check tomorrow after having cleared the error to check the same is re-generated..

Phil

p.s. think there is only 1 on this model.

[PhilH]

update:

after reconnecting to the scanner no error codes were present. played about with the crank case breather pipe (back of head) and found the engine note changed back to normal. therefore changed that hose for a new one. they come bunched with a water hose, so i seperated them. the old one was totally clogged and coaked with old oil and grime.

had to be the problem! with the new one fitted it ran like a dream...for about 2 miles anyway. now the old problem of the rough idling is back. when we ordered the breather hose from bmw they said it normally came with a valve..cyclone valve i wonder? the breather pipe goes into this round looking device which is part of the inlet manifold. now, my guess is that needs replacing so one is on order..

engine management light now comes on as it has a really hard time breathing at idle. perfectly fine throughout the drive (rev range) however.

update to follow.
phil

[PhilH]

Problem solved.

Replaced the 'crankcase breather vent valve' £32 from BMW. coupled with the crankcase breather hose made for around a £50 fix before labour.

Cheers,
Phil

[drz]

Oh man. I am so sorry nobody was able to chime in and help you solve your problem :-/ Thanks for coming back with updates, though. I am glad to see that the problem is solved.

- Daniel