I put a K&N performance air intake on my 05 250 5.4 and it started ot run really funny. Stalling now and again and just running crappy. Found out it was my mass air sensor and it had some oil from the filter on it which made it give the truck falty readings. So i cleaned the sensor and the filter (didn't use a that much oil on it) and still had the same problem. I even left it set overnight before I used it.

I put the stock air box back on because I didn't want to deal with the problems but I really like the K&N design. What should I do?

 

I'd just run a stock filter, not worth the hassle of too much oil getting into the mass air meter. I really doubt it's worth much HP or mpg anyway. I've run them on a lot a vehicles, but I've heard they don't filter as well, and I definitely oil mine too much.

 

I run them in all the cars I have. Never had the issue you are having though. I kept the stock filter and put that in while I let the K&N dry for 24 hrs. I've never noticed a difference in my Excursion or my 92 Z28 but we used to have a 2000 explorer with the 5.0 in it and on a trip to the Florida keys I picked up about 4 mpg.

 

I've never had any oil issues and I have used their filters on several vehicles.

 

Nope never. I even went from a drop in K&N for my 2003 5.4L F250 to the FIPK kit and it runs a little better now. No issue with oily MAF or dirt in the throttle body.

 

I also had an 05 with the 5.4 and had the same problem. A mechanic told me that it was the oil that came from the filter and got on to the mass airflow sensor.

 

Yeah that's the exact same thing I was told too.