K & N air filter

bcpianoman · #1 01-15-2010, 10:01 PM

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.

1986nate · #2 01-15-2010, 10:03 PM

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

bcpianoman · #3 01-15-2010, 10:06 PM

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

SoCal LS-L · #4 01-15-2010, 10:22 PM

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.

Blacky · #5 01-16-2010, 05:31 AM

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.

**Ewie** · #6 01-23-2010, 07:37 PM

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.