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Discussion Starter · #1 ·
K & N filters and MAF\'s

They are NOT compatable!

The oil from the filter gets on the MAF - Mass Airflow Sensor - and changes the characteristics.

I bought a 97 Astro van - it had the K&N already on it. I cleaned it and re-oiled it - then the trouble started.

It would run fine for awhile - 20-30 miles, then start running lean, no power, stumbling, etc. Shut it off for a moment, restart it would be fine for awhile again.

Apparently what was happening was on start-up the ECM causes the MAF to go through a "burn-off" procedure - the wire gets really hot to burn off butterflys, dirt OIL etc. That would burn off any traces of the filter oil.

Then during normal operation the slight oil fumes/mist from the filter would collect on the MAF's hot wire, changing it till it ran bad. Hot days it was worse.

I cleaned the filter housing and ducting and installed a stock type paper element. 200 miles later and still no more problem.

Who'd a thought?
 

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Re: K & N filters and MAF\'s

Well at least you practice what you preach.

[ QUOTE ]
Don't be afraid to try something new.

[/ QUOTE ]

And thanks for the info.
 

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Re: K & N filters and MAF\'s

K & N's have never worked for me. I had them in all my trucks. But they were just too much of a pain to clean. So, now they all sit on a shelf and the trucks have high flow paper filters.
 

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Re: K & N filters and MAF\'s

The K&N site only directly addresses MAF failure, which isn't what Rich was alledging.

They do suggest (but don't exactly say) that they couldn't get a filter to shed any oil; just that it didn't shed oil under the test they described. However it doesn't seem likely, in view of that test, that Rich's problem came from the filter shedding oil. At the same time, it sure does seem that that's exactly what his filter was doing.

Their site rather pointedly mentions their own oil many times. It doesn't seem likely to me, but what do I know, that there could be a difference in their oil that would keep it in the filter when other oils of similar viscosity would disperse in the airstream.

But oil does evaporate, although quite slowly in comparison to water, alcohol and gasoline. I wonder if their oil evaporates even more slowly.

Rich, what oil were you using?
 

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Re: K & N filters and MAF\'s

MAF sensors are extremely sensitive to outside debris. Back in the 1990's FORD had a terrible problem with their MAF sensors. They used a heated wire to measure the manifold pressure. The wire would get coated with garbage from incoming air. Once that the MAF wire was dirty the MAF would report incorrect pressure to the ECU. The ECU would react and the engine would run like garbage. If the owner was smart, they'd take an pencil eraser and wipe the MAF wire clean with every oil change.

Manufactures learned from the Ford error and did not mount the MAF in the TBI gullet. Some moved the MAF off the engine, away from debris and used a tube to come up to the MAF. If the incoming air is filled with an oil mist, it will still coat the inside of the MAF. The engine will still run badly.

Then the manufactures started to got to a Digital Read Out MAF. No longer analog, it is harder to diagnose (use a scanner) but is still subject to debris on the wire.
 

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Discussion Starter · #7 ·
Re: K & N filters and MAF\'s

It's possible that my "cure" was invalid. Anything's possible, it could have been the space aliens hiding behind the Hale-Bop comet causing it. But it's highly unlikely! (I almost always wear a hunk of tinfoil on my shirt to keep them away!)

I've put about 800 miles on it since - still haven't experienced the problem like before. She's running great, smooth, good power etc.

The oil I used, as well as the cleaner before oiling it, was from the official K&N cleaning kit. Their oil is red.

The K&N reply to it on the link - they say "failure" - the MAF did not "FAIL" - it apparently was just giving the wrong information, causing problems.
I didn't replace the MAF, I just cleaned it. I did not see any deposit on the hot wire itself (sensing portion) but the sides of the housing right next to the wire had a thin oily deposit on it. I rather doubt it only got on the sides without getting on the wire itself.

But remember the sides don't have the "burnoff" feature, they don't self clean. (Why would the engineers design in a "burn-off" feature if foreign matter on the wire has no bearing on performance?)

No MAF code was set - it was still working to the best of it's ability, it apparently just give slightly false information causing a lean condition.

Wiping the sides right next to the wire with a white rag revealed the deposit was red. (But could it have been those space aliens tricking me by spraying ATF on it?)
In fact, ALL of the ducting had that red oily film. When I'd previously cleaned the filter I'd cleaned it all as my standard procedure, so I know it had been clean.

The filter is a flat filter in the housing, air is drawn in from the bottom, goes through the filter, then up and out through a duct to the MAF, where it then goes through another duct to the intake manifold.

ALL the ducting had that thin film of redish oil, not alot, but it was there. I used brake cleaner to wash it out, (removed from the engine of course) then flushed it with 409 and water.

I even ran a rag down inside the manifild snout past the throttle body as best I could, and found that thin reddish film.

It could have been my mistake too - I might have over-oiled the filter. But I'd rather have too much oil, too much dirt capturing performance, than too little. Cleaning the MAF is preferred to sanding out the engine.

But don't get me wrong -- I am a believer in the K&N Filters - I run them on almost everything I have. My testing - although not done scientifically, have shown them to be far superior to others I've tried.

My test - use a paper element for awhile. Run a white paper towel down the snout or on the places AFTER the filter - carb air horn, ducting, inside the filter housing area etc - where only clean air is supposed to be. Notice the dust and dirt on the towel.

Now do the same test with the K&N - mine have always come out clean - or at least, much cleaner! Try it! Yes, you do get that slight oily residue, but that tiny amount of oil won't hurt anything (well, except a MAF obviously) - it may even help catch that stray dust particle that got through!

I'll still use the K&N's, just not with MAF sensors.

Note: The Air Temperature Sensor on those vans is also in the airstream right behind the MAF. That too may have been affected, as it had that oily film on it too. Could it be that was the culprit? I doubt it, I have a 95 Astro too with a K&N - the air temperature sensor is in the same place on it - but it doesn't use a MAF - it's the speed density system (MAP). It's never done it. BUT --???

As far as the ability to flow more air - the K&N may flow better - for the area of filtration, but if you still want a paper element, simply increase the filtered area. Use a larger diameter or taller element.

Remember - the internet doesn't reject words. Lots of sites claim the K&N is terrible (but notice theirs is always so much better.) Make your own test, draw your own conclusions.

He He -- I'm sure one can find an internet site that says the only way to have sex is once a year with whips and chains.
Make your own test, draw your own conclusons!
 

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Re: K & N filters and MAF\'s

[ QUOTE ]
He He -- I'm sure one can find an internet site that says the only way to have sex is once a year with whips and chains.

[/ QUOTE ]

crap... there's another way???
 

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Discussion Starter · #9 ·
Re: K & N filters and MAF\'s

Well, I think my cure was correct. My wife put about 1000 miles on it since I ditched the K&N. Then last week we took off on a mini-vacation - about 1100 miles more. So far not one stumble or problem, no Service Engine Soon Light - it ran great the entire time. 2100 miles total seems to prove it.

Mileage before was around 10 MPG with the K&N, on the trip it ran between 20 to 22 MPG.

The filter swap and spraying down the MAF with brake cleaner was the only thing I did.

Funny how a tiny detail like that can make such a huge difference.

I'm going to try putting that K&N back in - just to prove it.
 

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Re: K & N filters and MAF\'s

Yep. If you put the K&N back and the problem returns, it's pretty solid proof.

Was your driving different between the 10 MPG and 22 MPG runs? I can't imagine any simple change making that much difference unless it was running in closed-loop mode most of the time.
 

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Discussion Starter · #11 ·
Re: K & N filters and MAF\'s

It certainly would!

The circumstances the mileage was taken was very close to being the same.
Driving "before" was mostly local - but local here is highway mostly. Even a short trip to the closest supermarket is 15 miles down a 2 lane highway. The "before" was that kind of "local."
The mini-vacation ("after") was to Phoenix, Flagstaff, and Laughlin, then home - home is the California Desert near Palm Springs. Again, all highway.

The "before" it was intermittant, sometimes it ran fine, sometimes it would hardly get out of it's own way. No codes set in memory. I did "catch" it a couple of times when the SES light was on, the code said "lean." But if you cycled the key, the code went away without my clearing it.

The only way I could "catch" the code was to make it set, hook up the scanner while it was running, then quick cycle the key to download. If I waited a moment after shutting it off, then tried to download the code would dissapear.

Turn the key off, wait, key on - SES would go off and it would run better for awhile - then screw up again. I think it was when the ECM restarted it went through "Burn Off" - temporarily cleaning the hot wire.

Apparently after a minute or two of being off the ECM automatically went through it's cold start procedure and did the burn-off.

It runs sooooo much better now, lots more power - all the time, no stumble etc.

I'll put that filter back in just like it was when I took it out - I won't add any more oil on it. It'll be an interesting test.

I might even try something - kinda cheating in a way - I'll spray a tiny bit of the K&N oil directly on the hot wire when it's fully warmed and running fine.
 

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Discussion Starter · #12 ·
Re: K & N filters and MAF\'s

I guess I proved my guess.

Yesterday I put the K&N filter back on. I did not add any oil to it - the only thing I did was shake it off a bit. It was not very wet - in fact under other circumstances I would have given it quick spray of more oil.

Started up fine. I revved it up several times, no problem. I drove it around the yard a few times, no problem.
I drove it down the street - no problem.
I drove it up a short hill - oops - what's that? A misfire?

By the time I got to the top at, or near, WOT it was running terrible.
On the way back down the SES light came on.
I stopped by the side of the road, shut it off, waited a minute or two - restarted. (burn off)
Ran OK, no SES light.

Once I got it home (1 mile) I removed the filter again. Idling, I sprayed a fine spray of the K&N oil directly on the hotwire - just a tiny bit. It died!
I immediatly restarted it (no burn-off time) - it seemed to run ok at idle. Snapping it would feel like it had very little power.

Key off - wait 2 minutes, key on (burn off - I couldn't see it smoking or anything - but the lighting wasn't the best.
Start - ran fine again, snapped fine.

I cleaned the hot wire with brake cleaner (engine off, wire was cool.) Before I did that I ran a white paper towel around inside the intake snout. It looked clean in there, yet that white paper towel showed just a slight touch of red - the color of the filter oil. Hey, the filter element was oiled, but not sloppy wet, in fact, it barely came off on my fingers. For good filtration purposes I would have liked it to be even more oily!

I put in the paper element, and challenged that hill again at WOT. She ran up that hill like it was supposed to.
Went to town and back, 35 miles - ran great.

My conclusion is, despite K&N's denial, the tiny bit of oil from the oiled filter gets on the hot wire on a MAF sensor, changing the signal to the ECM. It's still functioning, so MAF codes themselves are not set - the MAF output is still in it's expected range, it's just giving wrong information.
Other codes will set because the engine is not recieving the proper air fuel mixture - it may run lean or rich. The ECM will try to determine the problem, but since it "sees" what it "thinks" is a normal reading from the MAF, it will try to blame other components - very misleading, and it can be very expensive chasing after it by replacing parts.

But --- You decide.

(But -- I'm still going to use K&N's on carbs and non MAF vehicles because of the excellent filtration. Flypaper has to be sticky to work.)
 

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Discussion Starter · #14 ·
Re: K & N filters and MAF\'s

A week ago a friend called - Pontiac with the MAF and K&N.
His symptoms were similar - stumble, poor performance etc.
I told him about what I found with the K&N.
He called again last night - fixed! Same cure, cleaned the MAF wire and put a paper filter in it.

This morning I was at a Chevy dealer trying to get a dash part for something else - talked to the service writer - he said he's seen it several times himself.

Now I'm wondering - the ducting AFTER the K&N, the inside of the intake manifold etc - they get a thin coating of the oil.
I wonder if even when it's a MAP sensor type, not a MAF type, could this fine oil deposit be affecting things like the MAP and Air Temp Sensors even though they are not directly in the airstream?
Could it be over time they end up accumulating enough of the filter oil - and any dust that may have got in - to affect them? Not enough to set a code or be called a "failure," but enough to get the mixture wrong?

Maybe K&N's shouldn't be used with any computer controlled system?
I'm going to do a little experimenting.

I also wonder what type of testing K&N actually did when they said they even submerged a MAF into their oil and it affected nothing. Surely it wasn't on a vehicle - submerging the hot wire into oil is going to radically affect the temperature of the wire just by heat absorption alone.

Makes ya wonder about everything they say.
 
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Re: K & N filters and MAF\'s

This illustrates the difference between short and long term testing.....
Installing the filter and then racing the car down the strip and saying it improves performance without any issues is not the same as driving that car for 20K miles and making the same statement.....

In the kind of work I do, just because it works on my desk fine does not mean it's going to work out in the field.......
 
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