Wierd K&N air-filter symptom..

[eddiealfanut]

Hi all,

This was a simple one to fix, but I'm just puzzled that I'm
getting the symptoms at all.
The story:

I had a free-flow air filter on my 75 TS LE, but decided to upgrade to
the K&N 57i jobbie as the existing one relied on a home-made and
non-too-elegant mounting solution.
As soon as the K&N went on, my idle went all to hell, dropping to
nearly stall, surging to 1800 and back again.
I did all the obvious stuff like checking for leaks etc. - seemed fine.
The AFM and idle by-pass were all fine before the K&N so I was confused.
However, as anyone who's fitted one will know, mounting the K&N setup
neccecitates rotating the AFM throgh 90 degrees so that it now stands
on its side rather than laying flat. So this morning I unbolted the
AFM from its mounting bracket and (with K&N filter still attached)
rotated it back to a flat position. Temporarily held in place with
cable-ties.
Guess what? Idle is now super-smooth once again....
But.... surely this would have cropped up before if this is to be
normal for rotating the AFM. I'm not the _only_ person ever to have fitted this kit to a 75.

So what gives?

Any ideas?

Ed.

[Craig]

G'Day Ed,

Which way up did you mount the AFM?

[Rookie ROX]

I have my AFM mounted on it's side in combination with a Unifilter foam filter and it works perfectly fine. The AFM is located with the plug facing upwards.

I've attached a picture of my setup for your convenience.

Edit: In hindsight though, I am using an AFM from a BMW 733i, however the only difference between that and the stock Alfa one is the size - the basic workings are the same, and it's using the Alfa electrics.

ROCK ON
R~R

[eddiealfanut]

Jeepers,

that's a far more salubrious setup than mine, but yes the orientation is the same with the plug and CO2 adjustment on the top......

still baffled...

Ed.

[AlfaVerde88]

There really can only be a couple of causes.

1. There is secondary air entering the system after the AFM, bypassing it, and creating a lean state

2. The airflap is not opening correctly for some reason

3. The way you have the connector twisted at that angle is exposing a current problem with the electrics. I had a Milano that had the AFM connecting cord melted by the exhaust and I had no idea until I moved the AFM one day.

Try rotating it 180 degrees so that the cover of the AFM is facing the engine and see what it does then.

[Craig]

G'Day Ed,

Quote:

Originally Posted by AlfaVerde88 2. The airflap is not opening correctly for some reason

[AlfaVerde88]

That was my first guess. The way you have it makes it work against gravity. Rotating it the other way makes it work with gravity and you will not have the oil collecting on the flap.

[eddiealfanut]

Thanks all for your suggestions. Iwill try them all in isolation to see. I like the suggestion of the oil from the free-flow, as I am a sucker for wD-40 (or its equivelant)and spray it around like confettti whenever anything needs fixing. :-)
Anyway, I will enjoy finding out what's at the bottom of this.

Ed

[Craig]

Quote:

Originally Posted by eddiealfanut as I am a sucker for wD-40 (or its equivelant)and spray it around like confettti whenever anything needs fixing. :-)

[eddiealfanut]

OK, it's official; Craig has obviously sold his soul to the God of automotive second guessing
Took off the original AFM and, sure enough, lots of black gunge making the flap a tiny bit sticky. Cleaned it all out with white spirits, and an immediate improvement in the idle.
It now behaves similarly to _both_ my spare AFMs. Really really smooth idle until operating temp just about hits 80+ (normal full temp) at which point it becomes progressively less smooth. Not anything like as bad as before, but intrusive enough to annoy. This is all with the AFM vertical. If I swap it back to horizontal I am sure it will be 100%. I'm still puzzled by this behaviour, so I need to confirm it (again).
Anyway, it looks like I'll just make up a new mounting bracket which allows the AFM to sit horizontally (which is the way it is on the spider too coincidentally).


Ed.

[eddiealfanut]

OK. Still makes no sense to me, but here's the conclusion.
Attached are two photos, first is the K&N filter attached as per their intentions, the second is with a mounting bracket I had to make.
I spent the entire weekend messing with this, so I can catagorically stand over my findings... with the minor caveat that they make no sense at all :-(
_If_ I mount the AFM vertically (first piccie) my idle is all shot to hell. I tried this at all operating temps, using a total of three different AFMs and they all behaved the same: cold idle, OK, warming (<40) not great, full op temp (>80) just woeful. (oh and I also tried a different filter, my previous one that used to work when mounted horizontally)
As soon as I mount the AFM horizontally again everything goes back to being peachy! I made up a new bracket, and used the flexible mounting bolts from the original air-box and everything is now perfect.
I still cannot believe that no-one has hit this problem before!
But for my motor, these are the facts.
Anyway, that's enough time spent on one filter change!


Ed.

[Capp]

eddiealfanut--

Well you're not the only one to have this problem of idle quality after re-positioning the AFM.
On my recently mostly completed twinspark into 105 GTV conversion I was stumped by surging hot idle, and in desperation replaced both idle air control valve and the throttle position switch. Turns out the IAC was fine but the TPS was bad electrically. Still no proper idle, so I took the expedient approach and plugged the pipe from the intake manifold to the IAC valve w/ a restrictor orifice which basically negated the IAC but let me have a proper warm idle that could be adjusted w/ the idle adj. screw. Cold starts are a bit of a challenge but acceptable for now.
Sounds like you may have hit on my problem also, but the correct mounting position is, alas, not achievable in the confines of the 105 engine bay without extending the throttle body bellows/inlet hose farther forward to enable me to lay the AFM flat, as intended. I'll report my findings soon. Thanks guys! All Alfa knowlege is eventually revealed, huh?