ELECTRONIC CONTROL SYSTEM
- Variable Resisto
r
VARIABLE RESISTO
R
This resistor is provided in D-type EFI systems and
L-type
EFI with optical Karman vortex type air
flow meter or hot-wire type air flow meter which
are not equipped with an oxygen sensor
. It is used
to change the air-fuel ratio of the idle mixture
.
OHP 3
5
Turning the idle mixture adjusting screw
clockwise moves the contacts inside the resistor,
raising the VAF terminal voltage
. Conversely,
turning the screw counterclockwise lowers the
VAF terminal voltage
.
When the VAF terminal voltage rises, the Engine
ECU increases the injection volume slightly,
making the air-fuel mixture a little richer
.
ELECTRICAL CIRCUITRY
Engine EC
U
OHP 35
®
NOTE
It is usually
not
necessa
ry
to adjust the idle
mixture in most models, provided that the
vehicle is in good condition
. However, if it
does become necessary to do so, always use
a CO meter
. If a CO meter is not available, it
is best
not to attempt to adjust the idle
mixture if at all possible
.
1
1
. In the vane type air flow meter, the idle mix-
ture can be adjusted by turning the idle mix-
ture adjusting screw in the air flow meter
.
(Some engines are equipped with air flow
meters which are sealed with an aluminum
plug
.
)
REFERENCE
Idle mixture
adjusting scre
w
In D-type EFI systems and L-type EFI with
optical Karman vortex type air flow meter
or hot-wire type air flow meter with an ox-
ygen sensor, the ECU uses the signals from
the oxygen sensor to correct the air-fuel
ratio of the idle muxture, so there is no
separate device for adjusting the idle mix-
ture
.
41
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