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PART 10-5 MOTORCRAFT MODEL 4300 CARBURETTOR
10-55
idle
full adjustments
are
made.
In
isolated cases, a satisfactory idle
condition
may
not
be
achieved
by
performing the normal procedures.
If
this
occurs, refer to Additional Idle Speed
and
Fuel
Mixture Procedures.
NORMAL IDLE FUEL
SETTINGS
-
ENGINE OFF
1. Set the idle fuel mixture
screw(s)
and
limiter
cap(s)
to
the
full-counterclockwise
position
of
the
limiter
cap(s).
2.
Back off the curb idle
speed
adjusting
screw (Fig.
19) until the throttle
plate(s)
seat
in the throttle bore(s).
3. Be
sure the
dashpot or
solenoid
throttle
positioner
(if so
equipped) is not
interfering
with
the throttle lever
(Fig.
20)
.
It
may
,
be necessary to loosen the
dashpot
or solenoid
to
allow
the throttle
plate(s) to
seat
in the throttle bore(s)
.
4.
Turn the idle
speed
adjusting
screw
inward until
it
just makes
contact
with the
screw stop
on the thottle
shaft
and lever assembly.
Then, turn the
screw
inward
I
1/2
turns
to establish
a
preliminary idle speed
adjustment (Fig. 19).
5.
Set the
parking
brake
while
making
idle
mixture
and
speed
adjustments.
NORMAL IDLE FUEL
SETTINGS
-
ENGINE ON
1. The
engine
and
underhood
temperatures
must be
stabilized
before
idle
adjustments
are
made. Run the
engine
a minimum
of 20
minutes at 1500rpm.
This can be done by positioning the fast
idle screw or cam follower on the kick-
down
step
of the fast
idle
cam
(Fig. 21).
2.
Check
the initial ignition timing
and
the distributor
advance.
Use an
accurate-reading tachometer and timing
light when
checking
the
initial
ignition
timing and
idle
fuel mixture and speed.
3. On vehicles with a manual-shift
transmission, the idle setting must be
made
only
when the transmission is in
Neutral.
On
vehicles
with
an
automatic
transmisSion, the idle
setting
is made with
the transmission selector lever in the Drive
range.
4.
Be sure the
choke
plate is in the
full-open
position.
5.
Turn the headlights on high beam
to place the alternator under a load
condition
in order to properly adjust to
the
specified
engine idle speed.
6. The final idle speed adjustment is
made
with
the
air
C()nditioner
(if
equipped) turned ON.
7.
Adjust the
engine curb
idle rpm
to
specifications.
The tachometer reading
(rpm)
must be taken with the
air
cleaner
IDLE MIXTURE
LIMITER
S
FIG. 18- Idle Fuel Mixture Adjusting
Limiter - 4300 4· V
installed. On vehicles with less than 50
miles, set the idle
speed
approximately 25
rpm below specifications to
allow
for an
rpm increase as the engine loosens up in
the first 100 miles of driving.
If it is not possible to
adjust
the idle
speed
with the air cleaner installed;
remove it, make the adjustment, then
replace the
air
cleaner and
check
again for
the
specified
rpm.
Manual transmission vehicles may be
fitted with a solenoid throttle positioner.
However this is not connected on these
engines and
must be
adjusted so
as not to
affect
the
engine
idle
speed.
Idle
speed
adjustment is
to be made on the normal
throttle
stop screw.
8. Turn the idle mixture adjusting
screw(s) inward
an
equal
amount to obtain
the smoothest
idle
possible
within
the
range
of the idle limiter(s).
Check for idle
smoothness
only with
the
air
cleaner installed.
ADDITIONAL IDLE SPEED
AND FUEL MIXTURE
PROCEDURES
If
satisfactory
idle condition
is
not
obtained after performing the preceding
normal idle fuel
settings,
additional
checks
of engine
systems
must be performed.
1.
The
following items
should
be
checked
and,
if required, corrected.
a.
Vacuum leaks
b.
Ignition
system
wiring
contmuity
c.
Spark plugs
d.
Distributor breaker point
."well
angle
e.
Distributor point condition
f.
Initial ignition timing
In certain instances, it may be possible
that the idle condition is not
as
good as
...
"'ltally
expected. It is suggested that the
customer with a new vehicle be
advised
that the vehicle be driven 50 to 100 miles.
MODEL 4300 4. V
FIG. 19- Curb Idle Speed Adjusting Screws
Then,
when the engine
friction
has been
reduced,
the
idle condition should
be
improved. If,
after
the break-in period, the
idle
condition
is
believed
to
be
unsatisfactory, re-adjust the
engine
idle
speed to
specification and observe for a
satisfactory idle.
2.
If the
idle condition
is not
improved after the items in Step I have
been
checked,
perform the
following
engine
mechanical
checks:
DASHPOT
LOCKNUT
BJ134·A
FIG. 20-
Dashpot
-
Typical Installation
a.
Fuel
Level
b.
Crankcase
ventilation
system
c.
Valve
clearance
(using
the
collapsed
tappet
method for hydraulic
valves)
d.
Engine compression
3.
After
verification of all engine
systems
has
been made,
there may be
isolated
cases where a satisfactory
idle
condition
has not been
obtained.
due
possibly
to
a
lean idle
fuel
mixture.
If this
condition
is encountered, refer to the
following operation.
REMOVAL AND
INSTALLATION OF
IDLE LIMITER CAPS
Should
the idle limiter
caps
need
replacement
because
of
deformation, muti-
lation or readjustment of idle mixture to
meet
emission
level requirements the
fo:'owing
procedure must be
adhered
to
as
the
'therm'll conductivity'
type
of gas
analyzer
found iri most
service shops
is
not
accurate enough
to give the required
carbon
monoxide readings
.
1. Remove the
air
cleaner.
2. Cut
the plastic limiter
cap ana
carefully
pry
apart and
remove it from the
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