Stalling after shifting, while slowing to idle in gear.

[amalventano at sc.rr.com (Allyn)]

> Alright, this has gone on lone enough.
>
> The  car ('84 rocco, 1.8 CIS) just dies after shifting. It used to be

reposted from my post from last september:

---------------------------------------------

The rieger does the same exact thing:
    our cars have an idle fuel cutout. if the throttle is at the idle
position,
it closes the switch on the throttle body. if the idle switch is closed and
rpm
> ~1600, this results in the jetronic box applying ~-50ma to the DPR until
rpm
drops below ~1400 rpm. This lets the engine coast down with no fuel (as
opposed
to the fuel injection attempting to supply correct fuel during a coast).
    as a side note, there is a time delay. the ecu must see the idle switch
closed for >1/4 second in order for it to start the idle kickdown process.

the reason we get our stall is a combination of any of the following:

- dirty idle contact, resulting in longer than 1/4 sec lag for ecu to see
the
switch closed (switch debouncing is accomplished by a r/c circuit in the
jetronic box), resulting in the kickdown occuring right at 1400 rpm or
slightly
below, possibly resulting in a stall if you get it just right.
- sluggish/clogged fuel system, resulting in a lag as the DPR attempts to
get
back to normal control pressure (<1400 rpm). if it cant get pressure back
quick
enough, you stall.
- vacuum leaks (may not be enough to mess with idle, but can be enough to
cause
a stall in this kickdown condition).
- tuning: the kickdown circuit recovers to the standard +5 to +10 ma DPR
current
range. if you adjusted/tweaked your DPR current out of this range, your
fuel/air
will be out of whack immediately following the kickdown. this may be enough
to
cause a stall.
- idle speed set screw adjusted too low. if the ISV is already at near max
open
dwell during a normal idle, it cant open any further to correct for the
downward
swing during a kickdown, meaning its harder for the system to recover a low
idle
speed, and you stall.

    and finally, the reason the problem goes away when the a/c is on: idle
kickdown is disabled with the a/c on to prevent compressor loading from
stalling
the engine during a kickdown event.

    I plan on messing with these things one at a time until i nail it, but i
am
fairly certain that its a combination of the above thats causing it right
now. i
have a feeling simply opening the idle speed set screw a bit will fix the
problem.

HTH
Al