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csupan 06-28-2007 03:03 PM

Oil in K&N filter ruined engine?
I went to Kragen to replace my air filter, and they didn't have the filter I wanted (regular OEM), so they sold me a K&N filter. A few days later the Check Engine light came on and my car stalled, not starting until I put in a fuel filter in the gas tank. Even then the acceleration was slow. I then tested the engine with the OBDII tester, and it said there was a problem with the oxygen sensor, so I took it in to my mechanic. To my utter horror, he said I need $2,000 worth of work on the engine because of the fact that the air intake was too strong for this type of oiled air filter. Is this a well-known issue? Is K&N aware of this? Is Mercedes aware of this?

gmercoleza 06-28-2007 03:22 PM

It is possible that your MAF could become contaminated which could alter the air/fuel mixture. Improper mixtures have been known to cause expensive damage such as cracked pistons from detonation (lean) and melted cats from unburned fuel (rich). I would never use a K&N in my car...

mbdoc 06-28-2007 03:34 PM

Too much oil on the air mass sensor CAN cause damage to any MAF..

manny 06-28-2007 05:24 PM

Find another mechanic,
He either does not know what he is talking about, or ripping you off. :mad:
When people " over-oil " a K&N filter ( after cleaning ), it can cause problems with your mass airflow sensor in the future.
Since you purchased yours brand new, it would NOT have been over-oiled.

tvpierce 06-28-2007 07:32 PM

There are lots of write-ups about K&N filters -- some positive and some negative. But even in the negative articles, all indications are that they flow just fine (maybe slightly better than stock). That their weak spot was their ability to filter fine particles... and the fact that the oil has the potential to wreak havock with MAF sensors.

I've never heard/read anything that indicates they flow poorly. In fact, they are used in lots of racing applications in which they're run at WOT for extended periods. If they failed, I'm pretty sure the racing community would drop them like a hot potato.

Your tech's logic sounds a little cloudy. I'd get a second opinion.

Just my 2 cents, arguably worth that.

Jeff Pierce

Larry Delor 06-28-2007 07:56 PM

Before you spend a ton of money, spend a little, and buy a can of Air mass meter cleaner, and give it a thorough spraying. (remove the protective grid - watch the snap ring, so you don't loose it).
Check our fellow member JimF's website This ought to answer a few questions.
Good Luck!

POS 06-28-2007 08:56 PM

That mechanic is a dumbass. Your engine may very well need a total overhaul, but your air filter has nothing to do with it.

PS - I've tested the K&N vs the paper filter and found that a new paper filter breathes better than a new K&N, but a dirty K&N breathes better than a dirty paper filter.

msethk 06-29-2007 01:33 AM

i too, was going to recommend buying some Mass Air Flow cleaner. I just checked it out at the local parts place. if i remember right it is made by cfc or cmf or something like that (they make a wide range of cleaning products like brake cleaners and carb cleaners etc) for right at $6 and change.

Hatterasguy 06-29-2007 01:40 AM

Depending on the model you have, which you didn't post you may have two MAF's. Its possible both could fail at once, but labor to change them should be almost zip. They take like 10 minutes to change. I can see $800, maybe but thats high.

Its pretty commen knowledge that an over oiled K&N can blow MAF's. Your post is one of many.

yal 06-29-2007 10:58 AM

Run don't walk away from this mechanic. If its an MB dealer run faster.

psfred 06-29-2007 10:57 PM

K&N filters have wreaked havoc on many engines. They are fine for racing, as the engine gets tossed after a couple races anyway. In road use they cause more trouble than they are worth. They do NOT adequately filter the air unless oiled enough to ruin the air flow sensor (and they only sometimes respond to cleaning). The dirt that goes through once the oil blows off will eat the rings, cylinder walls, and valve seats, although this won't be instantaneous. Under no circumstances are they as good as the factory air filter, ever.

The "cold air intake" kits are worse, resulting in significantly LESS airflow at partial throttle and up.

Unless you burned the valves or something, all you did was toast the mass air flow sensor. The O2 sensor fault is because the computer cannot control the fuel mixture to get the correct response from the sensor.

$2000 ain't a big amount -- if you were talking valves or pistons it would be at least twice that anyway. I'm guessing R&R intake, clean up, new fuel filter, new airflow sensor ($800 if it's a dime) and possibly a new O2 sensor (or two, or four). May need new plugs, too if they got burned by the lean mixture.


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