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Old 11-10-2012, 10:05 AM   #3
Registered User
Join Date: Jul 2009
Location: Mahopac, NY
Posts: 26
My Ride: 03' 330i
Rough Idle

I had the same problem in my 03 330i, after a ton of work I narrowed it to vacuum lines broken, one behind the Mass Airflow Sensor which leads to the fuel filter, and another on the air pump on the right front of the engine and wraps around the back of the engine. If that doesn't work check our youtube videos about replacing the oil seperator which is crankcase ventilation system which is an 8 out 10 on the DIY difficulty scale, it works wonders. You have to replace the unit and all the hoses, about $160 in parts. It is buried under half of the crap on the left side on the engine. They are known to go bad around 90k miles. If you get lean engine codes that is the tip off that you have vacuum and oil seperator issues. Good Luck
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