K & N air filter
 

A guy at the local Subaru autowrecker told me today that he has reason to suspect that the oil in a K & N air filter may cause premature failure of the MAF sensor. Chime in here if you've had a MAF sensor failure and let us know if you're using a K & N filter.

Re: K & N air filter
 

Won't cause it to fail but will cause it to be coated in the oil and cause inaccurate readings to the ECU causing problems;)

Re: K & N air filter
 

What this guy said is he thinks it causes the plastic to break down.

Re: K & N air filter
 

Nah, the MAF is solid-state and would have to experience some serious plastic warpage to have the output signal even slightly affected.

Im more of a fan of the high-flow filter being relocated into the fenderwell anyways, that way it wouldnt even be a concern.

Re: K & N air filter
 

I've used a K&N FIPK on my truck for 8 years and an oiled filter CAI on my wife's Vibe for 5 years with no issues at all except the one time I over oiled the Vibe filter and threw a CEL. I cleaned the MAF and it was fine.

Re: K & N air filter
 

I'd heed what he said.. I had this exact problem on my 2001 Legacy GT-B. I bought the car new and during a subsequent service I enquired about installing a K&N filter to improve "breathability". Long story short, the dealer sold it to me and installed it during the service. Everything was fine for about 6 months and then the car started running really rough and surging terribly. I took it back to the dealer a few times until finally getting someone with more experience to diagnose the problem as being a faulty MAF and that it was'nt under warranty as I had installed a K&N filter. I argued that they sold the filter to me and installed it and produced reciepts as evidence afterwhich they replaced the MAF as well as refunded the cost of the K&N and fitted a factory filter.

The problem is that the oil particals from the K&N (and other oil-impregnated filters) comes out of the filter material and deposits on the very fine sensor wire in the MAF unit eventually causing it to warp due to uneven temperature and potentially break (as happened to me) if left unchecked. The wire cannot be replaced or repaired and so the whole MAF unit need to be replaced, sometimes at significant cost.

Like others I had used K&N filters on previous cars for years and swore by them, but none of those vehicles had the MAF setup that any of my Subarus have.

Re: K & N air filter
 

And they let alot more dirt into your engine than a normal filter would.

This page is a good read if you are considering going to a K&N
http://www.duramax-diesel.com/spicer/index.htm

Re: K & N air filter
 

I prefer dry filters like Green, AEM, Apexi etc. Oiled filters can cause havoc on MAF sensor equipped cars. Though usually thats due to the owners coating them excessively with oil.

Re: K & N air filter
 

I've run a K&N filter for a few years in an '89 Honda, and have experienced no problems. However, recently I did send off an oil sample to one of the analysis companies, and the report came back that the oil had an unusually high level of silica. I'm thinking that the filter is not working as well as the standard paper filter, and that I'm not doing my engine any favors by leaving in the K&N. I'll send off another sample to see, and then if it's high, go back to paper, then send a 3rd and see if the silica has come down.

The late 80's Honda engines are famous for going 3 or 400k. Mine has 225k, and I'd hate to think I'm compromising it for the sake of a couple of extra hp.

Re: K & N air filter
 

And if you look @ the dyno numbers, in most cases the horsepower gains from air filters like that are usually AFTER your peak HP, so they're pretty much useless. Just some numbers to make the Johnny Andretti Eclipse/Civic owners think that $100 "cold air" intake, $80 fart pipe and $120 Erector set wing really make their car faster :lol:

Re: K & N air filter
 

Excellent link, sheds some light on something I always wondered about.

Re: K & N air filter
 

I never had any problems with my K&N filters. It's a good practice to clean your MAF every so often anyway. Usually I clean mine everytime I service the car. Plus since my filter's in the fenderwell I don't think it's as big of a deal.

That said I think I'll switch to an AEM dryflow sooner or later.

And STILL clean my MAF every once in a while. haha

Re: K & N air filter
 

This is a lot more than a good and should go into the how too stuff, or become a sticky. Please can someone make this happen.

Re: K & N air filter
 

A legitimate question: How much "dirt" is negligible, and how much is harmful? Anyone who's eaten anything has pretty much consumed some number of bugs or rat hairs, which is OK with the FDA if not one's own body.

Can we relate to the amount of dirt that actually gets through these filters? Remember, we're talking about enough introduced to suffocate the filter pretty well. That's some poor car maintenance - likely several oil changes, even in a reasonably dusty environment.

Take any given number of grams of dirt, remove the amount that the oil filter would remove, and divide it by the number of oil changes that your properly maintained car would have before its air filter was restricted to over double its resistance as new? Not much.

FWIW, I don't care how much the test stand cost. That seems like fluff, and in a third party article, it seems to want you to believe it's honest. That's shaky as a debate tactic. I'm not saying it's untrue; I'm saying that it seems to be trying hard to be seen as true. Please see disclaimer below. ;)

Re: K & N air filter
 

Good questions to be sure. I have found that anyone with an agenda can pretty much pick apart anything. Use what you feel comfortable with and whats readily available to you. I have used pretty much everything out there. Though I prefer dry filters only due to oil covered MAF's causing problems in the past (for me personally).

I have a Stock STi red panel filter in my SVX if that makes any sense! LOL