I popped a K&N air filter into my '07 RX8 to replace the OEM filter. After a few dozen miles of highway driving, the car started to hesitate and bog down, like it was getting no gas. Took it to a Mazda dealer and they blamed the aftermarket filter, saying it "contaminated the O2 sensor." Anyone heard of this? Was I supposed to wash the new filter before installation? Dealer said they cleaned things up, and replaced the filter with manufacturers and the problem went away.

Not only did this strand me in Brainerd for a day, but a missed a track day at BIR and had to pony up $200 for the dealer to tell me that the aftermarket filter had screwed things up.

I also emailed K&N, so I'll be sure to post their response.

 

By O2 sensor you mean the MAF sensor. Yes you clean, dry, oil, dry. But you failed

 

There is an O2 sensor on the exhaust manifold and on the catalytic converter - both therefore post-combustion.

I'm at a loss as to how an intake filter adversely affected either O2 sensor.

The filter comes pre-oiled from the factory and only needs to be recharged when cleaned. If you oiled it yourself to such a degree that the MAF got coated that could be an issue, but barring that again I'm at a loss to understand the dealer's complaint.

Anyway, as you know K&N provides a toll-free number for the dealer to call should any such silliness arise.

edit: I s'pose you could have gotten a bad filter that didn't pass much air at all, in which case the MAF would send low airflow data to the ECU and in turn affect performance. $200 just to install an OEM paper filter and perhaps spray the MAF with some cleaner!!!??? But then a dealer charged my daughter $50 to reset a loose gascap CEL, so ....

 

I've been running a K&N for a couple seasons now and when I recently removed my MAF for inspection it was fine (although I of course sprayed it with electronic cleaner anyway since I was there).

 

I can vouch for the K&N panels being oiled well already when new....

i got rid of my drop in K&N panel.... i'd never had oil in my intake before or since, as per what CRH said i did NOT oil the filter when i put it in. in a tank of gas or two i had already started seeing MAF readings change from normal and fuel trims with it. when i pulled the filter out there was no buildup like the guys who have engine oil in the accordian, but there was definately an oily residue that was not there prior to the K&N filter. maybe mine was too well oiled? lol

 

Everything is a tradeoff.

Related, I use a farily expensive anti-allergen (more restrictive) air filter in my home HVAC unit in the Winter and early Spring, but its airflow is not really adversely impacted due to the lighter warm air. However, I go with an inexpensive (lower restriction) filter in the Summer due to the heavier A/C'd air.

The oiled K&N is certainly better at trapping contaminants and its cotton fabric is supposedly lower restriction than the paper, but it does make me speculate that perhaps the OEM is similarly better in the Summer.

Of course over-oiling the K&N is an issue (or oiling the wrong side!).

 

You take your car to Brainard International Raceway and you don't have the simplest mechanical ability?

Your asking for trouble.

By the way... how's the new track.

I'm gonna take my 8 up there someday.

I use to race bikes up there back in the day........

 

Not sure I would put the maintenance of MAF sensors under the category of "simplest mechanical ability." My "simple mechanical abililty" to put a new air filter in is what makes me dangerous.

K&N called and said they had never had a complaint about residue from a new filter mucking up an 8. I'm going to email him a copy of everything.

 

For anyone that is curious, K&N vigorously denies that their filters can effect the Mass Air Flow Sensor, and has posted their position at http://www.knfilters.com/MAF/massair.htm

They have offered a consumer protection pledge that they will not allow their customers to be charged for a repair because of this. Per their request, I just emailed copies of the invoices to them.

So it leaves me wondering WTF? The car ran fine for the 120 mile trip back to the cities, so whatever it was seems to have resolved. I had originally told the stealership that it seemed like the car was not getting gas, and that the gas tank and filler pipe had just been worked on, and my guess was that the recent work had stirred up crap in the tank and gunked up the fuel filter. That is what I had orignally asked them to check, but they blamed it on the air filter and tried to blame me for not putting premium gas in the tank.

Anyway, thanks everyone for your two cents.

And if anyone tries to charge you for damage supposedly done by a K&N filter, call K&N immediately!

 

That is a method I usually frown upon...
Those are axial resistors and if someone applies too much pressure on the body, those leads can break.
Or if the leads allow a small amount of bending, what potential difference in resistance will this produce?

I can always walk over to one of our thru-hole placement machines and grab some axial resistors and test the force needed to bend those leads under tension.
Never know... it could just be me being over-paranoid.
Its why I tell people to just spray the wires instead of touching them.

 

K&N filter and their oil does NOT **** MAFs up, but a factory filled K&N filter MIGHT have this problem. cuz at the mass production line, they just dump the whole filter into a pond of oil, then move it around to let it "self" drip, which also means its overfilled from factory

This is why every single K&N filter that I got, I will ALWAYS clean them, then re-oil it by hand, before I use it.

 

^^ Gotta peg the rare BS meter on that one nycgps. It's only oiled on the outdoor air intake side from the factory.

I cleaned and 'recharged' mine once this past early Spring and no MAF residue when recently inspected.

Also concur with just spraying the MAF and not actually contacting it.