[BruceJ]

Originally Posted by se4y

Thank you very much for read my thread and your advice. I looked up dictionary and can not find "cel"means what . Does CCV means closed crankcase ventilation ?Would you pls give me more information(z4 e85 2008 ) Should I change o2 sensor first? thanks a lot for your time and help

Yes, CCV means Closed crankcase ventilation. If you have a 3.0 engine http://www.realoem.com/bmw/showparts.do?model=BU33&mospid=49304&btnr=11_3738& hg=11&fg=15

O2 sensor is last thing I would test/replace
I would check:
1. Air Intake filter dirty?
2. Disconnect/ reconnect MAF sensor looking for change in idle. If idle gets worse when disconnected then MAF probably okay
3. Is the rubber intake boot intact, no cracks?
4. Test each coil - while engine is running disconnect/reconnect each one individually. No idle change while disconnected means coil possibly bad.
5. Are there any vacuum leaks, broken/disconnected vacuum hoses?
6. Is the CCV system intact? Cold weather and time will cause cracks. if so this causes a lack of vacuum that can cause poor idle, excessive oil burn, fouled plugs, etc
Good luck
Bruce