BMW Repair: Fuel consumption & spark plugs, mass airflow meter, oil seperator

Question
Evan,

I have a 2000 528i, I replaced all spark plugs about 3000 km back & now when I inspected the plugs, the threads are moist, the top thread has a bit of oil & the plug also has carbon deposits. The car runs fine otherwise, no RPM problems, no pickup or rough running problems, I also had the compression checked which turned out fine.

I do have a fuel consumption problem, could this indicate that the engine is running rich & perhaps I need to check the O2 sensors? The car takes 2/3 tries to start on cold mornings (I live in Sydney) & the engine stutters a bit before resuming a regular rhythm.

Thanks.

Answer
Janak, Replace O2 sensors at 100K miles. I would inspect the idle valve for resistance of movement and the intake hose that connects to it for tears reguarding the starting problem. Also look to the Mass Airflow meter for proper reading (14-17 kg/h is normal with no A/C running). Check the crankcase vent valve (PCV and oil seperator) for integrity to make sure no oil is getting in the intake manifold. If there is oil in the spark plug bores then replace the valve cover gaskets and grommets. There are some things to check.
-Evan