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Discussion Starter #1
HI

Anyone have any feedback on using K&N Filters on a M54 engine? Twice now I have had two different service shops tell me we should not use K&N Air filters on my M54 engine because it is not designed for it, and can mess up the metering read by the MAF.

I've used K&N filters on cars, marine diesels and even an aircraft engine, and I have never run into this before.

Anyone have any insights you can offer on this? For now I put the paper element filter back in my 2002 M54.

Appreciate your throughts.
 

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Nuclear engineer
02/2012 X5 35d M57Y CPO 98K miles NOKIAN WR G3 12K miles
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That is correct, there is no benefit to using an aftermarket engine air filter. Your stock filter - silencer's first job is to protect your MAF, to send it clean oil free air (that's the white fluffy part's job). The MAF itself does a fine job screening trash from the engine.

A MAF works by comparing the heating power to two sensitive elements, one not in the air stream and the other in the air stream. They are both heated quite hot. If oil gets on the exposed element it bakes into an insulating varnish throwing off the calculation. Solvents tough enough to remove the varnish are tough enough to remove erode etch the sensitive element. Late model HFM MAF are particularly susceptible. The film is very fragile.

My VW TDI went 180K miles on the OE MAF before I sold it for safety reasons.
 

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Discussion Starter #3
Well, that would definitely explain why my MAFs seemed to be failing prematurely - message received. No more K&Ns on my M54.

Thanks for the feedback.
 

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I switched to a KN on my E53 4.6is and within two weeks I was having issues with my MAF (at 75K miles). Cleaned it over and over and got it working again. Put my airbox/muffler back in along with my suction hood and haven't had one single issue since. So, I would say that my experiment with a ram KN was not successful. Based on your MAF issues, I would suggest yours wasn't either.
 

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Yup - I just spent a couple weeks chasing down some issues with my 2002 M54 engine. I was getting ICV errors, and E3, E4 errors - replaced PCV system, vac hoses, cleaned injectors/plugs, removed intake and cleaned it out, replaced a few sensors, ICV and vac control valves etc. Last thing I did that wound up clearing all the codes, was changed the MAF which was only 18 months old! None of the codes I was seeing seemed "MAF specific" and given it was reasonably new, I did not try changing it. Lesson learned.
 

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Discussion Starter #6
I switched to a KN on my E53 4.6is and within two weeks I was having issues with my MAF (at 75K miles). Cleaned it over and over and got it working again. Put my airbox/muffler back in along with my suction hood and haven't had one single issue since. So, I would say that my experiment with a ram KN was not successful. Based on your MAF issues, I would suggest yours wasn't either.
Yup - you are absolutely spot on - one would think I would have learned my lesson from before. I ran into this (same car) years ago, but forgot about the K&N being the cause. Put it back in and within 6 months the MAF failed. All the other work I did troubleshooting the issue has paid off too however - this engine is running beautifully now.

One thing I did do when I removed the intake manifold (I took it off to replace the PCV) is I removed all the injectors. I was going to send them to get tested at a shop. Instead I cleaned them myself with some carb cleaner, and then tested the spray pattern by making a connector from a harvested plug (junk yard) and a 9V battery. Once the valve is opened with the battery you can spray carb cleaner through. I wound up replacing two of the injectors that did not have what I would have called a clean spray pattern with harvested ones.

My M54 is running like it should again.
 
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