K&N Cold Air Intake Issues
 

*off topic, this is my first post!*

So I bought a K&N cai for my FR-S a few weeks ago (This one). I had my roommates help me install it, since I had never done anything like that before (It was really, really simple and I practically redid the installation for reasons I will soon explain). Turns out, they didn't screw the MAF sensor in all the way, and left the coupler really loose around the intake pipe, triggering my check engine light several times.

Anyway, after I fixed those problems, everything appeared to be running fine. However, recently I have noticed some strange things happening. First of all, my mileage has decreased. I went from averaging 28 in the city to averaging at BEST 26; I am hovering right around 25. Second, when my rpms hit about 3k they drop down to like 2.5-2.7 regardless of whether or not I am staying on the gas. Any ideas as to why these two things may be happening? Maybe I am just inadvertently driving a little harder (hence the mileage) and the rpm dips are completely normal?

Note: I have an automatic transmission, but use the paddle shifters all the time. I'm wondering if that has anything to do with the rpm drops?

Once you are 100% certain that you have the intake installed correctly and leak-free you should disconnect your negative battery lead for a few minutes and press the brake pedal to reset your long term fuel trims which were screwed up while your intake was incorrectly installed. Allow a few days for the ECU to adjust the LTFT and everything should normalize.


As for your trip computer calculated mpg, that calculation is affected by many factors including LTFT so I wouldn't worry about it at all. As for the rpm drop that is the torque converter locking up and perfectly normal. Just one of those things that we tend to notice when watching for problems after modding. Nothing to worry about.

Sounds like

1. MAF sensor not installed correctly or air leaks.
2. MAF sensor damaged or dirty, try cleaning with maf sensor cleaner
3. You may need to rescale MAF sensor due new intake, this is generally required if the diameter of the intake tube differs from the stock size or the intake changes the flow around the MAF sensor

see here http://www.ft86club.com/forums/showthread.php?t=64790

You car will generally run with a changed intake but if maf scaling is effected or airflow arround maf is turbulant ir will run a bit rich/lean and may exhibit some drivability problems like your experiencing.

Holy crap the description on the site you linked is full of marketing BS.

Anyway, welcome to the forums :thumbup:

Make sure everything is tight and that there are no air leaks first of all. If that is all good you may need a tune as per steve99's suggestion. You are new here you won't know that most aftermarket intakes are generally a waste of time and money for the 86/FRS/BRZ and that many need a tune to work as smoothly as the stock intake unless the time has been taken to ensure the MAF housing reads similar to the stock unit.

I am not sure about the K&N intake specifically. The MAF may be spot on or it may not. Even if it is not it may be close enough for the ECU to adjust. As Fast_Freddy mentioned you are best resetting the ECU and driving it around for a couple of weeks to see if it will adjust enough before forking out for a tune. Having said that a tune is a good thing to have, it really wakes the car up :thumbsup:

For just an intake he should not need a tune, and as far as ECU learning that should "at MOST" take a few hours not weeks for sure.

Does the drop in rpm happen every time you go to 3k? Maybe it's just the torque converter hooking up, which is completely normal. You might not have noticed it before prior your mod, because you're less aware of things. Personally whenever I install something new I always have a period of uneasiness... I always think any rattle or something of that nature is something wrong LOL... though it's probably always been there.

Thanks for the replies guys. I did disconnected
my negative battery terminal during installation and left it disconnected for about 30 mins after. I did not do anything with the brake though, I will definitely do that soon.

As far as a tune goes, I don't really think it's worth the money right now. I plan on doing my exhaust this summer so maybe I will get a tune after that, when the effects of it will be worth more.

The RPM dip usually happens when I'm in 2nd or 3rd and is pretty consistent. The only time I don't notice it is when I keep pressing the accelerator (not holding it at one point).

The brake part as well as bs about ltft over a few days was wrong.

Don't know why a mod deleted my previous post saying the same thing.

Dude glad i saw this, i installed the same CAI and a Borla Cat-Back exhaust. My buddy [who tuned cars and works on them] told me i dont need a tune my car is fine. But i asked around to other people and they say yes[we highly recommend].... if i dont get a Air/Fuel tune done will anything happen? Is the tune just to get max performance out of aftermarket parts? Or will the ECU read whats going on and balance everything outto the MAF? Im new here so any help would be appreciated i really dont want anything happening to my car. Thanx!:bonk: