[Diy_efi] Audi idle issue

[David Allen]

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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