[Diy_efi] Audi idle issue

Tue Feb 28 01:44:20 UTC 2006

Top reply:

Many thanks for taking the time to go thru this is detail, David.  I'll get
a helper over tomorrow and give this a try!

Right for Rich, Left for Lean?   Nah, that'd be too logical...heh.   I'll
have a look in the book - now that I now what I'm looking for.

Also the tip about the O2 sensor, much appreciated, as mine may be bad.
Good to know it will default to a running state with sensor unplugged.

Ernie

----- Original Message -----
From: "David Allen" <davida1 at hiwaay.net>
To: <diy_efi at diy-efi.org>
Sent: Monday, February 27, 2006 7:03 PM
Subject: Re: [Diy_efi] Audi idle issue

> The K-jet "toilet bowl" has a tapered housing below the plate.  The more
air
> the engine draws in, the farther down in this tapered housing the plate
will
> move.  The fuel distributor increases fuel flow as the plate draws down.
If
> you make the plate sit higher in the toilet bowl with the engine off, it
> will press the fuel distributor in further (more fuel) when the plate is
> drawn down by a given airflow.  That adjustment adjusts the linkage
between
> the plate and the valving in the fuel distributor.
>   Ok- this should ballpark adjust it. It has been a long time and many
many
> miles since I did this so you may have to work out some details. Before
> anyone flames me please re-read this statement! :-)
>   If the engine runs only when the cold start valve is open, it is
probably
> running too lean to run without this extra fuel.
>   Since the idle mix adjustment is already off-base, set it to an
> intermediate position for a starting point.
>   Unplug the O2 sensor. This should make the system default to a "neutral"
> feedback trim on the mixture control solenoid. (someone correct me if I am
> wrong on this - it's been a while)
>   Start by manually pressing the airflow meter flap down (in the same
> diretion that airflow draws it when the engine runs).  Press it down and
> find a position where you can hold it by hand to make the engine idle.
(have
> an assistant or use a remote starter button)  If you can make it idle by
> pressing the plate down, then you know that an adjustment here will
correct
> the problem.
>   Mark a line on the inside of the "toilet bowl" housing at the edge of
the
> plate with the engine off and the plate fully up.  Adjust the screw and
> release the plate.  Continue adjusting until the plate now rests just
above
> the line (line hidden below plate) with the plate fully up and engine off.
>   See if idling is possible without pressing on the plate. Repeat small
> adjustments until engine idles.
>   Once you have it idling okay, test drive it.  Look for signs of obvious
> lean running such as hesitation or pinging.  If it does seem lean, move
the
> adjustment to raise the airflow plate higher up in the housing (draw
another
> line and cover it up). Repeat until you have the engine running OK when it
> is above idle, then use the idle adjustment mixture screw to dial in the
> idle.
>   Moving the airflow flap afects AFR across the whole range including idle
> therefore this has to be adjusted before adjusting the idle.
>   Another point to ponder - on some K-Jet systems (not sure about yours)
the
> AFM flap has to be drawn down some to actuate the fuel pump relay.  If the
> adjustment of the plate is SO far off maybe the arm doesn't move down far
> enough to actuate the fuelpump relay?
>   Most of the systems I worked on were on BMW, Mercedes and Saab so there
> may be details that differ on this car.
>   Good luck!
> David
>
>
> ----- Original Message -----
> From: "Ernest Buckler" <ebuckler at icehouse.net>
> To: <diy_efi at diy-efi.org>
> Sent: Monday, February 27, 2006 4:02 PM
> Subject: Re: [Diy_efi] Audi idle issue
>
>
> > >   Using a helper to press down the airflow meter flap to keep the
engine
> > > idling, fog each area listening for the engine speed to increase.
> >
> > >   Why did you need to adjust the CO adjustment?
> >
> > David,
> > Thanks for the extensive advice, will double check all those areas - I
> have
> > a new boot (old one was cracked, as you mention - but the car still
> ran...),
> > new hoses, new clamps, clean ISW, new thermoswiitch, new ign. wires, new
> > dist. inner parts.   The car ran fine once warm but very rich at idle
> (black
> > smoke, etc) so I was trying to adjust mix with the only means I knew
(idle
> > screw did nothing, even after total bench cleaning of throttle plate,
> > resoldering of bad joints inside that switch) - which was the air flap
(CO
> > adjustment, therefore the overall "jetting" (mixture) adjustment,
> according
> > to my thinking??   In frustration, I turned it a LOT, trying to get
> > something to change that rich idle.  Nada.  But - my Duh here - then I
> > discovered that the throttle switch plug was not in tight, had fallen
out.
> > Now it's plugged back in, BUT the engine won't run after cold start
shuts
> > off.  No more black smoke - no smoke at all...  And I have been told
that
> > the air flap screw is normally adjusted in tiny fractions of a turn -
> > whereas I could be 3 or 4 or 5 turns out, no way of knowing what I did
in
> my
> > frustration (above).   To much random action, not enough thinking things
> > thru on my part.  The Bentley manual gives a method for getting the
basic
> > air flap setting, but it requires removing the air boot, and that was
such
> a
> > PITA to install, I'm hoping there's a "tune by ear method" that'll get
me
> > close enough to drive the car to an emissions shop for final tweaking.
> > Thanks for any clues,
> > Ernest B.
> >
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