# K & N AIR FILTER causing check engine light?



## Passat18901 (Jan 16, 2009)

For some reason the guy at my dealers VW parts counter thinks that a K & N filter on a CC will cause engine faults and cause the check engine light to come on when it gets slightly dirty.
He said that owners come in with K & N filters and engine faults and they recommend that the owner throw them away and go back to the OEM filter.
Can this really be true? 
Anyone using K & N filters?
I am thinking of using a K & N filter when I replace my OEM filter.


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## Aonarch (Dec 4, 2006)

Passat18901 said:


> For some reason the guy at my dealers VW parts counter thinks that a K & N filter on a CC will cause engine faults and cause the check engine light to come on when it gets slightly dirty.
> He said that owners come in with K & N filters and engine faults and they recommend that the owner throw them away and go back to the OEM filter.
> Can this really be true?
> Anyone using K & N filters?
> I am thinking of using a K & N filter when I replace my OEM filter.


He is wrong. Obviously you need to clean the filter, but no it won't through a code.


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## Passat18901 (Jan 16, 2009)

Thanks Aonarch! 
That's what I thought. 
It only makes sense to keep the filter clean.


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## CC'ed (Dec 1, 2009)

Actually, he is right. There are many instances (on many different makes of cars) where a K&N filter has contaminated the MAF sensor due to excessive oil that mists off the K&N element, and then bakes onto the hot-wire (or hot-film) airflow sensor. This contamination film causes the airflow signal to be incorrect (versus the actual amount of air flowing), which will set a CEL code if this error gets too great. Often times the excessive oil is due to over-oiling the element when it is cleaned. In my opinion, the small airflow gains of a K&N is negligible, and of not much performance gain, especialy considering that poorer dirt filtering capability (and risk of MAF contamination) of these types of filters. Don't waste your money, save it for an ECU tune upgrade.


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## DavidPaul (Nov 28, 2009)

CC'ed said:


> Actually, he is right. There are many instances (on many different makes of cars) where a K&N filter has contaminated the MAF sensor due to excessive oil that mists off the K&N element, and then bakes onto the hot-wire (or hot-film) airflow sensor. This contamination film causes the airflow signal to be incorrect (versus the actual amount of air flowing), which will set a CEL code if this error gets too great. Often times the excessive oil is due to over-oiling the element when it is cleaned. In my opinion, the small airflow gains of a K&N is negligible, and of not much performance gain, especialy considering that poorer dirt filtering capability (and risk of MAF contamination) of these types of filters. Don't waste your money, save it for an ECU tune upgrade.


Actually you are wrong and he is just not up to speed on this procuct. It's kind of sad actually, since he claims to be an Auto Tech.

When the K&N drop in filter is installed, new, there is never a problem. It's only when the newly cleaned filters are installed that the problems can sometimes begin.

Once in a while an owner, after cleaning the filter, will put too much Oil in the filter and cause the MAF problem. This is not the fault of the filter.

This is an operator/installer problem which doesn't have to happen if a little caution and following of instructions is exercised.

I am capable of following instructions and exercise caution when cleaning and re-oiling. As a result, have never had a single prolem since the K&N filters were first introduced.

By the way, how long have you been using them? Just asking because I am curious about the extent of your personal experience with the K&N drop ins.

I am never too old to learn from some one else's experience.


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## CCRlineBlack (Apr 6, 2010)

CC'ed said:


> Actually, he is right. There are many instances (on many different makes of cars) where a K&N filter has contaminated the MAF sensor due to excessive oil that mists off the K&N element, and then bakes onto the hot-wire (or hot-film) airflow sensor. This contamination film causes the airflow signal to be incorrect (versus the actual amount of air flowing), which will set a CEL code if this error gets too great. Often times the excessive oil is due to over-oiling the element when it is cleaned. In my opinion, the small airflow gains of a K&N is negligible, and of not much performance gain, especialy considering that poorer dirt filtering capability (and risk of MAF contamination) of these types of filters. Don't waste your money, save it for an ECU tune upgrade.


This is true!


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## Track5tar (Feb 16, 2010)

CC'ed said:


> Actually, he is right. There are many instances (on many different makes of cars) where a K&N filter has contaminated the MAF sensor due to excessive oil that mists off the K&N element, and then bakes onto the hot-wire (or hot-film) airflow sensor. This contamination film causes the airflow signal to be incorrect (versus the actual amount of air flowing), which will set a CEL code if this error gets too great. Often times the excessive oil is due to over-oiling the element when it is cleaned. In my opinion, the small airflow gains of a K&N is negligible, and of not much performance gain, especialy considering that poorer dirt filtering capability (and risk of MAF contamination) of these types of filters. Don't waste your money, save it for an ECU tune upgrade.


I agree. Our cars rely so much on measured air and the maf and oil don't play well

This is another reason to get dry filters. Just FYI, forge wintake and twintake uses dry filter


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## Sammzway (Aug 14, 2011)

K&N filters are reusable and should be recharged using the rechargeable kit after certain miles. On my 350Z I was always scared to clean my air filter because of using too much oil, it was easy to damage the MAF from excessive oil. I always used JWT filter and swapped out for a new filter every 30k miles. Never had an issue. The only problem I can think of (from my experience) was MAF sensor issue.


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## Tsquared (Dec 9, 2011)

CC'ed said:


> Actually, he is right. There are many instances (on many different makes of cars) where a K&N filter has contaminated the MAF sensor due to excessive oil that mists off the K&N element, and then bakes onto the hot-wire (or hot-film) airflow sensor. This contamination film causes the airflow signal to be incorrect (versus the actual amount of air flowing), which will set a CEL code if this error gets too great. Often times the excessive oil is due to over-oiling the element when it is cleaned. In my opinion, the small airflow gains of a K&N is negligible, and of not much performance gain, especialy considering that poorer dirt filtering capability (and risk of MAF contamination) of these types of filters. Don't waste your money, save it for an ECU tune upgrade.


I'm on this side. Used one on my Z for about 20,000 miles, and I was always paranoid about oiling the MAF sensor, and did I have enough oil on it to actually do some filtering. Ultimately decided it just wasn't worth the hassle for an extremely minor power gain and a little more intake moan.


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## Passat18901 (Jan 16, 2009)

Track5tar said:


> I agree. Our cars rely so much on measured air and the maf and oil don't play well
> 
> This is another reason to get dry filters. Just FYI, forge wintake and twintake uses dry filter


K & N states that there is no proof after many investigations that their filters will foul the MAF sensor and it should not void the warranty.

http://www.knfilters.com/audio/automotive/11_Vehicle_Warranties.mp3

Maybe the only problems are when people clean the filters. 

A K & N filter is only $37 for a CC. 
I would not bother cleaning it for that price since improper cleaning may be the cause of any issues. Chuck it after 30-50K and get a new one.

Still a little concerned but I will be switching my stock filter for a K & N anyway, living on the edge. :facepalm:


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## CC'ed (Dec 1, 2009)

So, lets see :
Risk of MAF contamination
Minimal if any gain in horsepower
More dirt into the engine
Intake sounds a little more aggressive
$40

I would not buy/use one.......


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## ElectricCo (Jul 19, 2001)

i used a k&n on my se-r and on my jetta 1.8t. both cars threw check engine lights with the k&n. the nissan threw one both before it was cleaned and after. the jetta threw one about a year after i installed it. i swapped it out for an itg filter and never had a problem for as long as i owned the car.


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## Passat18901 (Jan 16, 2009)

ElectricCo said:


> i used a k&n on my se-r and on my jetta 1.8t. both cars threw check engine lights with the k&n. the nissan threw one both before it was cleaned and after. the jetta threw one about a year after i installed it. i swapped it out for an itg filter and never had a problem for as long as i owned the car.



OK, everyone has pretty much convinced me that using a K & N filter may not be a good idea. Thanks for the input on this subject.

What do you think about this ECS Tuning replacement PAPER, not oiled, air filter. 
http://www.ecstuning.com/Volkswagen-CC-FWD-2.0T/Engine/Intake/ES1866664/

It's cheaper than the OEM.


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## EngTech1 (Nov 30, 2008)

Passat18901 said:


> For some reason the guy at my dealers VW parts counter thinks that a K & N filter on a CC will cause engine faults and cause the check engine light to come on when it gets slightly dirty.
> He said that owners come in with K & N filters and engine faults and they recommend that the owner throw them away and go back to the OEM filter.
> Can this really be true?
> Anyone using K & N filters?
> I am thinking of using a K & N filter when I replace my OEM filter.



LOL - then that Mechanic pulls it out of the Trash , cleans It and sells it on E-Bay : LOL

I agree with the fact that most clean them Wrong , best to Not clean them at all .
There are the same type out there that have 5 layers instead of the 2 or 3 K&N has .

Anyone running in a very dusty area with these CAI systems should be running Bags
Covers on there - Cold Air Kit .

Same with If Your one of these Drivers - that are Running in a Lot of - Road Spray traffic
in the Dusty & Salty Rain Grim . _*Better Bag It !*_


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## Aonarch (Dec 4, 2006)

CC'ed said:


> So, lets see :
> Risk of MAF contamination
> Minimal if any gain in horsepower
> More dirt into the engine
> ...


Where are you getting your data on more dirt?

Out of an independent test the K&N filter earned 2nd in the least amount of particulates, with the stock filter material containing 498 particulates vs. 501 for the K&N. 

I can back up my argument with data... Can you?

MAF contamination is from operator error. Follow the directions of the recharge kit and you will have zero issues. I've been using K&N filters for at least 10 years.


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## old guy2 (May 30, 2010)

I've given up on the K&N filters. Installed one on one my Jetta's as well as a 2.8 VR6 Passat. I ended up replacing the MAF sensor in both cars. Coincidence? Possibly. Just not worth the extra $$ for negligible (if any) performance gain over an OEM or dry foam filter.


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## CC'ed (Dec 1, 2009)

Aonarch said:


> Where are you getting your data on more dirt?
> 
> Out of an independent test the K&N filter earned 2nd in the least amount of particulates, with the stock filter material containing 498 particulates vs. 501 for the K&N.
> 
> ...



I would think K&N would publish the results of a dirt filtration test if it showed good performance for their filter......


Read this scientific test of air filter performance:
http://www.nicoclub.com/archives/kn-vs-oem-filter.html

" In the chart above it’s important to note the different test durations for each filter. The AC Delco filter test ran for 60 minutes before exceeding the restriction limit while the AMSOIL and K&N tests each ran for 20 and 24 minutes respectively before reaching max restriction. 

In 60 minutes the AC Filter accumulated 574gms of dirt and passed only 0.4gms. After only 24 minutes the K&N had accumulated 221gms of dirt but passed 7.0gms. 

Compared to the AC, the K&N“plugged up” nearly 3 times faster, passed 18 times more dirt and captured 37% less dirt. See the data tables for a complete summary of these comparisons."


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## old guy2 (May 30, 2010)

A lot of reading. Draw your own conclusions: *Clicky click*

Cliff notes version: *You have to decide for yourself whether you value ever last ounce of power or filtration. I cannot, nor will I make this decision for you. I do know that on a relatively stock car with a properly sized air filter, you indeed have very little if any performance to gain by swapping filtration material. *


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## Aonarch (Dec 4, 2006)

CC'ed said:


> Please provide a link to this dirt filtering comparison test. I have never seen any published data. I would think K&N would publish the results of a dirt filtration test if it showed good performance for their filter......
> 
> 
> Read this scientific test of air filter performance:
> http://www.nicoclub.com/archives/kn-vs-oem-filter.html





old guy2 said:


> A lot of reading. Draw your own conclusions: *Clicky click*
> 
> Cliff notes version: *You have to decide for yourself whether you value ever last ounce of power or filtration. I cannot, nor will I make this decision for you. I do know that on a relatively stock car with a properly sized air filter, you indeed have very little if any performance to gain by swapping filtration material. *


This.

Bob has good data on his site.

CC'd I do not care, nor will I waste my time beating a dead horse. This has been discussed thousands of times on forums.

I use K&N filters. I am an ASE certified tech and I have never had an issues in probably 10 years. 

Make your own decisions OP.


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## CC'ed (Dec 1, 2009)

Aonarch said:


> This.
> 
> Bob has good data on his site.
> 
> ...


Your ancedotal experience is not a valid substitute to a scientific comparision of filtering performance.


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## Aonarch (Dec 4, 2006)

CC'ed said:


> Your ancedotal experience is not a valid substitute to a scientific comparision of filtering performance.


Example 1

http://www.bobistheoilguy.com/airfilter/airtest3.htm


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## CC'ed (Dec 1, 2009)

Aonarch said:


> Example 1
> 
> http://www.bobistheoilguy.com/airfilter/airtest3.htm


Your opinion should be based on the standardized test that the entire automotive industry uses to measure engine air filter performance, not on an uncontrolled test based on the shade of color of the exposed filter samples.

" The ISO 5011 Standard (formerly SAE J726) defines a precise filter test using precision measurements under controlled conditions. Temperature & humidity of the test dust and air used in the test are strictly monitored and controlled. As Arlen learned in attempting his own tests, there are many variables that can adversely affect filter test results.A small temperature change or a small change in humidity can cause the mass of a paper filter to change by several grams. 

To obtain an accurate measure of filter efficiency, it’s critical to know the EXACT amount of test dust being fed into the filter during the test. By following the ISO 5011 standard, a filter tested in Germany can be compared directly compared to another filter tested 5 years later in Rhode Island. The ISO 5011 filter test data for each filter is contained in two test reports; Capacity-Efficiency and Flow Restriction"


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## Testiclease (Jul 26, 2010)

For what it's worth, I have had great experience with k&n filters.

I have a complete k&n CAI on out CC right now have run it for about 50K km and not a single problem. I live 2 km off the highway on a gravel road, and this damn city is under construction all year round. The CAI gave a noticeable bump in tow end torque and a bit better fuel mileage, most noticeable on the highway, which is the majority of our driving. I have cleaned an oiled the filter twice with no issues.

I also have one on my motorcycle, as it is the only filter that has not been punctured by debris, and has great gains on the bike.

I have used them on many vehicles over the past ten years with not one problem.

I not trying to endorse them, but talking from my experience they work great, and for the major dusty conditions our car sees i prefer the oiled filter, even if it may be a little more work to maintain.

On a side note about the Maf's baking the oil, should the air really be getting hot enough in an intake tube to actually bake oil onto the surface of the sensor, seems a little far fetched to me. if so, the filter may not be your problem.


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## Testiclease (Jul 26, 2010)

and i should mention that the k&n CAI on my dads FJ cruiser, made a huge difference in highway passing power.


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## Aonarch (Dec 4, 2006)

Testiclease said:


> and i should mention that the k&n CAI on my dads FJ cruiser, made a huge difference in highway passing power.


Kill the charcoal secondary filter in the box, makes a huge difference.

-Former FJC owner.


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## CC'ed (Dec 1, 2009)

Testiclease said:


> For what it's worth, I have had great experience with k&n filters.
> 
> I have a complete k&n CAI on out CC right now have run it for about 50K km and not a single problem. I live 2 km off the highway on a gravel road, and this damn city is under construction all year round. The CAI gave a noticeable bump in tow end torque and a bit better fuel mileage, most noticeable on the highway, which is the majority of our driving. I have cleaned an oiled the filter twice with no issues.
> 
> ...


As a certified auto technician you should know that the MAF sensor (the hot wire), or hot film is heated, and thats what bakes the oil contaminant oil.


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## Testiclease (Jul 26, 2010)

CC'ed said:


> As a certified auto technician you should know that the MAF sensor (the hot wire), or hot film is heated, and thats what bakes the oil contaminant oil.



i never said was i a certified auto tech. because i am not


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## Das Borgen (Sep 10, 2008)

Aonarch said:


> He is wrong. Obviously you need to clean the filter, but no it won't through a code.



ctually, the service guy is potentially correct

I've had 2 MAFs die on 2 different cars (an AAA 12V VR6 engine and an S5232 3.2L I-6 engine) because of K&N filters....the oil from the K&N gets on the MAF element and decreases the MAF performance and can potentially kill it

OEM (or any paper filter really) is best.....keep it


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## Aonarch (Dec 4, 2006)

Das Borgen said:


> ctually, the service guy is potentially correct
> 
> I've had 2 MAFs die on 2 different cars (an AAA 12V VR6 engine and an S5232 3.2L I-6 engine) because of K&N filters....the oil from the K&N gets on the MAF element and decreases the MAF performance and can potentially kill it
> 
> OEM (or any paper filter really) is best.....keep it


Read the rest of the posts.

The K&N filter right out of the box should not cause any damage to the MAF. Over-oiling while cleaning can.

OP get a dry filter if you are concerned. Companies like aFe might have a Pro Dry.


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## nixon_jetta2.5 (Jan 5, 2009)

There are rights and wrongs. What the counter rep dint tell you is that its not the filter its just the reo-oiling that causes it. But why just not go with an AEM or any other company that offers a dry filter? they are so much better. The K&N out of the box messed up the MAF on my old 2.5l Jetta, but 2.5l's are notorious for having a delicate MAF with an aftermarket intake.


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## Das Borgen (Sep 10, 2008)

Aonarch said:


> Read the rest of the posts.
> 
> The K&N filter right out of the box should not cause any damage to the MAF. Over-oiling while cleaning can.
> 
> OP get a dry filter if you are concerned. Companies like aFe might have a Pro Dry.


I bought both brand new and failure happened under 5k miles later in both cases

I cleaned both MAFs with MAF cleaner and codes came back and both MAFs died.....................

just reporting personal experience


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## EngTech1 (Nov 30, 2008)

*Like This : Only this Link is Cheaper*

Just - Bag It !

http://www.amazon.com/Shop-Vac-9011500-Super-Performance-Filter/dp/B0000CBJIH


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## Das Borgen (Sep 10, 2008)

EngTech1 said:


> Just - Bag It !
> 
> http://www.amazon.com/Shop-Vac-9011500-Super-Performance-Filter/dp/B0000CBJIH


that completely negates the performance advantage of a K/N filter and likely flows less that stock........at which point you're getting superb filtration


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## Tom333 (Nov 2, 2010)

Passat18901 said:


> OK, everyone has pretty much convinced me that using a K & N filter may not be a good idea. Thanks for the input on this subject.
> 
> What do you think about this ECS Tuning replacement PAPER, not oiled, air filter.
> http://www.ecstuning.com/Volkswagen-CC-FWD-2.0T/Engine/Intake/ES1866664/
> ...


I didn't read all the post but I tried the drop in filter (k&n) I didn't notice any gain really. IMHO ill stay with stock and it feels better actually. I also tried an open filter set-up (OEM still feels better for daily with stage 1).


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## EngTech1 (Nov 30, 2008)

*In the Nasty Weather - with Rain Grime or Road Dust - I'd be Bagging those CAI*

In the Nasty Weather - with Rain Grime or Road Dust - I'd be Bagging those CAI systems .

Stock Filter has a lot of Cross sectional Filtration Area Material .

If You really look at the amount of Pressure Drop it's not that much .

A CAI system usually includes a :Better - Smoother Design - increasing the Eff%
what Gets Me is then they turn around and put a little Skimpy Filter with the Kit .

You Wish to see some Real Filters & Trumpets : http://shop.grahamgoode.com/ggr-conical-shaped-group-a-kn-air-filter-ggr064-63304-p.asp

If Your Tuned and Pulling another 150 CFM on top of the 250 CFM a stock motor does (Approx)
Then Your beyond the Stock Design :


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