Toyota COMPUTER-CONTROLLED SYSTEM Training Manual page 87

EFI - Functions of Engine EC U
LS
signa l
Correction
ratio
Decreased Increase d
Engine ECU
Large
Target
curren t
Smal l
OHP 57
Idle
mixture
adjustinc
scre w
OHP 5 7
D-type EFI without oxygen senso r
L-type EFI without oxygen sensor but with op-
tical Karman vortex type air flow meter or
hot-wire type air flow mete r
The ECU also reduces CO emissions by
controlling the injection volume in accordance
with the engine speed .
RELEVANT SIGNA L
• Lean mixture sensor (LS)
OHP 5 7
CO EMISSION CONTROL CORRECTION
(D-type EFI'' and L-type EFI'z )
The injection volume can be adjusted by
manually adjusting the variable resistor (See
page 41) . This can be used to adjust the volume
of CO emissions .
RELEVANT SIGNALS
• Variable resistor (VAF)
• Engine speed (NE )
NOTICE
It is usually not necessary to adjust the idle
mixture in most models, provided that the
vehicle is in good condition . However, if it
does become necessa ry 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 .
REFERENCE
When the voltage of the terminal VAF is 0 .1 V
or less or 4 .9 V or more, the Engine ECU discon-
tinues CO emission control correction .
Variable resistor
77