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Discussion Starter #1
Hey, I finally figured out why my 2004 Z4 3.0 SMG was running rich in Bank 1 and Bank 2 It was the k&n air filter. Removed k&n air filter replaced with stock air filter . No more rich condition and no more SES light !!!!!!!! I know a lot of people use the k&n filter and have no problem, guess my car just did not like it. Later all !!!
 

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Official Bangle Hater
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Don't a lot of Cold Air Intakes (CAI) use K&N filters?

I have always been hesitant about running a K&N on a Mass Airflow car...
 

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That makes no sense. The MAF is what measures your air intake. You get into a lean situation when additional air enters your system without the MAF measuring in (somewhere between backside of MAF and intake runners. The K&N may well have allowed more air to be drawn into your engine, and your engine managmenet system was not able to compensate with enough fuel to offset the increased air flow. Perhaps you have an issue with your fuel system not being able to deliver an increased fuel flow. Perhaps you've got one or more fuel injectors that are dirty. Also, your fuel management system "learns" the fuel and air mixture ratio, and after a couple of hours of use and it self-adjusts (assuming you don't have other fuel or intake leak issues).

David
 

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Discussion Starter #5
Yea, I know it did not make sense to me either. But, thats my story and I'm stick'n to it ! You can also check the Z4-FAQs and How-tos section it has a post about this in it. Later.
 
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