K&N Filter Causes MAF Sensor Fault Code
 

Hey guys, over the weekend my cars Check Engine Light CEL went off and after doing a quick scan it appeared that the MAF sensor was the issue. However, after taking the sensor out and giving it a good cleaning I checked the filter and the new K&N filter I put in end of last season appears to be saturated in oil blocking air flow. Lucky I kept the old Porsche filter which I just cleaned it up well and placed back in the car for now.

Does anyone know how I can remove the oil off the K&N filter? Paid a small fortune for this filter and it's now causing issues with the car... it would be nice to clean it up so I can actually use it. IDEAS ?

Did you oil it before you put it in?

Oiling the KN is how it's supposed to work. I'm not a fan and won't use them. The paper filter is so much better filtration.

Too much oil on the filter...I use one on my pick up for the last 6 years and 70K miles without issue.

They sell a filter service kit, follow the directions to the letter and make sure you wipe down the rubber gasket after re-oiling to remove any residual oil on that piece. Part number K&N 99-5000

A little better than 20 years ago I used to run a flow bench. K and N were becoming very popular touting all kinds of performance benefits and better filtering. After testing them I would never use one. We could not use them on the flow bench (well not oiled anyway) as it would damage our equipment. The 1hp gain or so that you might have got from the "free flowing" element was quickly wiped out after just a few miles when your intake tract was coated with oil residue and slowing the air flow down and required intake manifold removal and cleaning to reverse. I am personally not a fan and could not tell you if they have changed in the last 20 years as I would not touch one with a 10 foot pole. Oh, and stay away from purchasing a car that has had one in it, having worked in the auto service industry I can assure you that 99% of people who run a K&N on their cars do not take it out and clean it or reoil it at anywhere near as often as necessary.

To answer your question, take the filter out and wash it off with a hose. Then you're ready to re-oil. Use less oil than previously and let it sit for a while before replacing it so the excess oil can run off.

I never oiled the K&N filter - I installed it straight out of the box as is... never added any oil to the filter.

We are talking about this filter...right??

It usually come pre-oiled.

K&N 33-2773 Replacement Air Filter, Replacement Filters

Then the oil has to be coming from somewhere else, failing AOS?

And I've never known them be pre-oiled tbh, normally have the oil in the box with it. Then again it's a long time since i used one of those pieces of ****************, Green Cotton filters for a long time now.

From my understanding the K&N filter comes pre-oiled...

That's new then, looks like it was over oiled then. They really are crap.

What filter would you recommend I use (2001 Box S) ? Link ?

I use a Green Cotton one, works perfect.

I stick with a Mann/Mahle/Hengst paper filter. Does a far superior job filtering dirt than the K&N (ran one in a VW turbo I used to own - not doing that again).

The AOS line enters the intake system behind the throttle body and into the intake.

ALL K&N filters come pre oiled, which can lead to MAF fouling. And while expensive as Hell, they really do not add anything to the car's performance.

The free flowing air filter is "achieved" by letting air in through larger openings in the filter element. Both Consumer Reports and Road and Track (IIRC) did tests several years back and the K&N let in more dirt and bigger particles of dirt than stock filters. While these may not have been Boxster based comparisons, the results from two sources with no axe to grind made me a believer that I shouldn't use the K&N.

I thought it was common knowledge that K&N filters are nothing but hyped garbage that will foul everything in the intake. :confused:

Do yourself a favor and dispose of it. ;)

And that is using a new K&N and oiling it, most people who pop in the filters don't service them often by washing and reoiling them making them even worse.

Exactly that. No entirely sure why people still use these POS, lot better options out there.

I called K&N and they said they would offer me a refund but I need to provide them a copy of my invoice.... sadly I did not keep it. If anyone has a spare invoice toss it my way please!