[snivilous]

Please don't give me too much shit, this is more of a thread to help other people if they are thinking about a cold air intake (CAI).

I have been running a K&N CAI for almost 2 years now. It was a mod that was added before I really got into modifying the truck very much, and it was a result of some issues with the stock system not sealing and getting some crude in it. My dad had had good experience with K&N way back when, and I run their air filters on my stand up jet ski with no issue so it seemed like a good move though I didn't do much research at the time because I wasn't very involved with the 4Runner yet.

The intake is nice from the perspective it has a mean growl to it which I've come to like, and that I just have to clean it instead of replacing the filter (in retrospect it's probably cheaper for the amount of time to just replace a filter than go through the cleaning/drying/oiling process).

However, last summer on my way to USU to help a professor with some classes I had the MAF go out on me. We cleaned it and had no issues for 100 miles and then it died again so we replaced it, and then no more issues. This may or may not of been influenced by using an oiled filter, I never over oil the K&N but it's something to consider...

Now on to the main point of this thread. This weekend I went mudding with @Cartzo and some other guys, our version of mudding consisting of muddy trails and giant puddles. After hitting one puddle really hard, I had a sudden drop in power as is associated with lack of air for the engine. Sure enough, the filter was totally wet and struggling to breathe.

This is not a current picture but from a few months ago, it illustrates how the K&N is setup and as you can see in the bottom left, the filter is completely open to the elements (unlike the stock system):



I was not entirely surprised the engine was starving for air based on the design of the intake, but after waiting awhile and the engine doing well we moved on. Fast forward and I my check engine light comes on when we are driving back, engine is running fine so diagnose it that my MAF is dirty and I use a scanner to confirm that. Yesterday, I go to pull the MAF to clean it and this is what I find:



Pull the filter and this is what my "filter" was NOT filtering out:



I have now removed the intake tube and this is my throttle body before the throttle plate:



I am going to write to K&N and throw some shit, because their supposed filter doesn't appear to do anything! I can understand it bogging down when it's wet, but letting sand and mud through the fabric filter is beyond me. Obviously I'm going to swap the stock unit back in now, until some point in the future when I can get a full on snorkel. However I can't recommend K&N any more, it works fine on my jet ski but that's operating in a clean environment where there is only water unlike my 4Runner.

Cartzo and I are planning to drive to CO from UT for spring break this Friday, which is a 500 mile drive. I am very concerned with the condition of my engine from all the shit that may of made it into the cylinders. I don't want to even drive it to a car wash to get the mud off (which has caused other issues that need to be sorted by Friday). As of now I will be pulling the throttle body and intake manifold and trying to clean as much of the intake system as I can.

I'd rather not see people being snotty and saying "I told you so", the CAI worked fine driving around town, but now that I go offroading upwards of 3+ times a week in conditions from snow to heavy mud and and pond sized puddles the K&N is showing its flaws and why I won't run it anymore.

[02SE]

Edit.. I didn't read your entire post, but the pictures say it all.

Just an FYI, I've seen muddy water make it's way through every kind of air filter made. OEM or otherwise.

I'd guess you were plowing through some mud puddles at speed.

That same muddy water can also be forced past any and or all of the numerous grease and oil seals on your 4Runner.

It's an ill-advised thing to do, if you care at all about the longevity of your 4Runner.

[JayRolla]

Any cold air intake will suck water in more easily. My buddy has had many issues in water with his KN.

[turbo8]

Just saying: it's an air filter not a water filter.

[LMR]

I've had the K&N CAI kit on mine for over 10 years with no issues. I have the PreCharger on the filter to keep it dry. It also keeps me from having to clean the filter after every time I'm been out wheeling.

K&N Air Filter Wraps

[rubbertoe]

Sorry about the issue sniv.these gauze filters will not stop water and i would suggest a pre- filter to slow down muddy water ingestion at the very least.if you ever hold a k&n up toward the sun a look at the amount of light let in you will also understand how it can also let small debris dirt and water also.this is how their get the better flow # . I am running a k&n in my sealed airbox and i will be putting pre-filter material inside the deck plate mod when i do it (ordered & waiting on its arrival ).to be honest i am kind of newer here on this site.but i don't always take everything i read on a forum or elsewhere as gospel especially when it comes to modding a great functioning system to begin with ( not saying you do , just mentioning to others on the subject ). i also own a first gen tundra and according to the tundra guys the cold air intakes are a waste of cash, with only a very small performance gain fro the big $,and the stock intake is plenty good for a stockish motor . newwer to the 4runners but have been riding mx ,sxs ,quads,jet skis for a good number of years .good luck man ! maybe a better preforming filter on the end of your intake may be an option also ,Uni ????

[NateMob]

It's well documented that K&Ns aren't worth a damn in the dirt.

If you can see light shining through it, how could it possibly filter microns of dirt and dust?

[T4R2014]

K&N filters suck but I don't think my OEM air filter will do a very good job at filtering mud either. I would've thought twice before driving through mud with an open air filter like that.

[MStudt]

Originally Posted by turbo8

Just saying: it's an air filter not a water filter.

I'm stealing this line!

[rubbertoe]

i am going to do something similar to this pictured (not a 4runner airbox lid ,but you get the idea ) inside a deckplate lid, to to keep all my my stock airbox qualities. snivilius i would wipe up as much dirt as you can by hand and try and clean up the tb.also you might want to take your intake manifold off and see how much made it inside your engine by the look of the ports. idk. its up to you how far you think you should go,but i'd imagine your engine is going to be alright. but you wouldn't want to do that very often (clogged injectors ,worn rings ,failed sensors ,ect..)But hey, at least your having fun ! (envious hahaha)check out the filter in the pic on bottom. fits in a 3rd gen that coupled with an deckplate airbox mod and some pre filter material over the opening i imagine would be a winning upgraded intake combo !

[bpowa]

K&N or any other hi performance filter will suck in fine dirt.. The only thing stopping it is the oil cleaner you should have pit on every so often.

I would use it only because I dont live around a concrete juncle.. Not much dirt here.. But for offloading I would use a conventional paper filter.

[thebrandon]

Not to be mean, but I would love to see the face on the person that gets your email complaint about how the filter failed under the circumstances and the way your whole motor looks. I'm sure being the company they are they will do what they can to make it right.

Sorry to see that this was the result, but mud and fine dirt will make it through just about any filter, especially a "high flow" filter like this.

Also mud is bad.

[downpour11]

I read your first post and skimmed the rest.. but, I HATE my K&N. I put it in because my stock air box crumbled to pieces. For my 96, that's the only aftermarket air filter I saw that was offered. I haven't had any MAF problems but my gripe is partly the oiled filter, but mainly how the damn thing attaches. Mine won't stay on the intake tube and keeps falling off, so I've resorted to duct taping the thing on. It gets dirty as hell every single trip, blah blah blah. Anyway, find a stock air box, or at least put a sock on the K&N. These filters suck in so much crap.

[snivilous]

Thanks for the advice guys, I have the stock intake at home still so I'll swap that in and maybe install a multi layer filter in the fender.

I understand it's not supposed to filter water, but I figured at a minimum it would keep sand and dirt out. If Trophy Trucks can run these types
of filters through the desert behind 20 other trucks throwing dirt and dust up, I would think it would be able to keep those kinds of particles out.

Pulled the intake manifold halves and throttle body.





Still shit on the lower manifold or whatever it's called between the valve covers.



It's caked on so I'm not too worried since none of it is loose to fall into the engine (by not worried, I mean it'll be fine without being taken
apart in the parking lot in front of my dorm). I'm going to power wash the intake manifold and then hand wash the throttle body and get all the loose dirt out.

I understand mud, puddles, etc. are bad and not helping the 4Runner. However, I use it as a means to have fun--even if that means pushing
the limit then so be it. I figure I'm a good enough mechanic I can fix whatever happens and I enjoy working on it anyways. Whatever doesn't
kill it means it will be upgraded that much further and come out more capable and reliable than it started!

[nor_cal51501]

So here's my experience with my K&N that I had on my 4runner for the first year I had it. For the first year I kept getting p0171 codes about twice a month. Then I supercharged it and the code came up immediately along with running horribly. Swapped a factory box back on and boom, runs like a champ and no more p0171 codes.