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post #1 of (permalink) Old 07-31-2006, 12:03 AM Thread Starter
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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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post #2 of (permalink) Old 07-31-2006, 12:37 AM
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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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post #3 of (permalink) Old 08-01-2006, 08:36 AM
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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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post #4 of (permalink) Old 08-01-2006, 09:17 AM
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Re: K & N filters and MAF\'s

Did a quick search on this:

http://www.knfilters.com/MAF/massair.htm

http://www.autoblog.com/2005/09/07/h...-filters-work/

EDIT: not trying to prove or Disprove what Rich has found, just interesting reading. I've used K&N's for sometime, but come to thinkof it, none of the vehicles I've used them on had MAF sensors. I've always kinda wondered about well they do actually filter.
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post #5 of (permalink) Old 08-01-2006, 10:14 AM
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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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post #6 of (permalink) Old 08-01-2006, 11:28 AM
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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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post #7 of (permalink) Old 08-01-2006, 12:35 PM Thread Starter
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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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post #8 of (permalink) Old 08-01-2006, 01:17 PM
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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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post #9 of (permalink) Old 08-07-2006, 12:09 PM Thread Starter
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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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post #10 of (permalink) Old 08-07-2006, 01:26 PM
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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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