[Diy_efi] Audi idle issue

Tue Feb 28 04:27:20 UTC 2006

   Good point about the plugging of the idle mix adjustment hole!
   Another thing that can happen is a SEVERE backfire can bend the linkage
between the plate and distributor. The reverse flow from the backfire will
force the plate "the wrong way" and if it comes up farther than the damper
mechanism allows for, the linkage can bend.  This will cause a severe
rich-idle condition, with the black smoke and fouled plugs. If the bend
isn't too bad, you can adjust it and restore it to proper operation.
  I would expect an intercooler full of gas fumes, igniting could qualify as
a "severe backfire." Under normal conditions, fuel is not in the
intercooler, but after sitting stopped, injectors could leak a little and
the fumes can fill the intake blumbing.  Any little "cough" during cranking
would ignite this unintended fuel/ air charge.
  Just another $0.02 worth!
David

----- Original Message ----- 
From: "Bill Shaw" <b.shaw at comcast.net>
To: <diy_efi at diy-efi.org>
Sent: Monday, February 27, 2006 5:48 PM
Subject: Re: [Diy_efi] Audi idle issue

> Was Audi still using K-jet in 89?  I thought Ferrari was the last
> manufacturer to use that mechanical injection stuff!
>
> One thing that messed me up setting CO with the 308's K-jet the first
time,
> you have to remove the allen wrench and plug the hole then wait a couple
of
> seconds before you can get a good reading,  otherwise you have an air
leak.
> At first it seemed like the changes were not having any effect,  but once
I
> started plugging the hole after each adjustment I could just dial it in
> perfectly.  Where are you Ernest?  My 4 gas analyzer would help if you're
> near CT.
>
> Bill
>
>
> > From: "David Allen" <davida1 at hiwaay.net>
> > Reply-To: diy_efi at diy-efi.org
> > Date: Mon, 27 Feb 2006 19:03:48 -0800
> > To: <diy_efi at diy-efi.org>
> > 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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