Toyota COMPUTER-CONTROLLED SYSTEM Training Manual page 83

EFI - Functions of Engine EC U
AFTER-START ENRICHMEN T
Immediately after starting (engine speed above
a predetermined rpm), the Engine ECU causes an
extra amount of fuel to be supplied for a
predetermined period to aid in stabilizing engine
operation . The initial after-start enrichment
correction is determined by the coolant
temperature, and the amount gradually falls
thereafter at a certain constant rate .
When the temperature is extremely low, this
enrichment roughly doubles the injection
volume .
1 .0
r
-------------------------------
0 *
Low ~ (6 O
A
-
Hig h
Coolant temperature °C (°F)
Depending on the engine models .
-RELEVANT SIGNALS
• Engine speed (NE )
• Coolant temperature (THW)
OHP 5 6
REFERENCE
In some engine models, the starter (STA)
signal is used as a condition for beginning this
correction .
WARM-UP ENRICHMENT
Since fuel vaporization is poor when the engine
is cold, the engine will run poorly if a richer fuel
mixture is not supplied .
For this reason, when the coolant temperature is
low, the water temperature sensor so informs
the Engine ECU, which increases the amount of
fuel injected to compensate until the coolant
temperature reaches the predetermined
temperature .
When the temperature is extremely low, this
enrichment roughly doubles the injection
volume .
Low
-
60" ~High
(140 )
Coolant temperature °C (°F )
Depending on the engine models .
-RELEVANT SIGNA L
• Coolant temperature (THW)
OHP 5 6
REFERENCE
In some engine models, the amount of this
enrichment changes slightly when the IDL
signal goes on or off, and it also changes in
accordance with the engine speed .
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