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Old 01-23-2010, 07:37 PM
**Ewie**'s Avatar
**Ewie** **Ewie** is offline
Aussie in enemy territory
 
Join Date: Nov 2009
Location: Auckland, New Zealand
Posts: 303
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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.

Last edited by **Ewie**; 01-23-2010 at 07:40 PM.
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