IDLING STABILITY CORRECTION
(
D-type EFI only)
EFI - Functions
of Engine EC
U
The fuel injection volume is increased or
decreased in accordance with changes in the
engine speed in order to achieve idling stability
.
In order to do this, the injection volume is
increased when the engine speed drops, and is
decreased when it rises
.
RELEVANT SIGNALS
• Engine speed (NE
)
• Thro
tt
le position (IDL
)
REFERENCE
In some engine models, engine idling is
detected by the change of the intake manifold
pressure (PIM) signal
.
HIGH-ALTITUDE COMPENSATION CORRECTION
(L-type EFI with vane type
air flow meter or op-
tical Karman
voltex type
air flow meter only
)
The density of oxygen in the atomosphere is
lower at high altitudes
. As a result, the amount of
intake air flow measured by the air flow meter
becomes greater than the amount of oxygen ac-
tually being taken into the engine
. This means
that if the fuel were injected under the same condi-
tions as at sea level, the air-fuel mixture would
become richer
.
For this reason, the ECU corrects the fuel
injection volume based on signals from the high-
altitude compensation sensor and the air flow
m ete r
.
This correction decreases the injection volume
by about 10% at 1000 meters above sea level
(for example)
.
101
.3 kPa
(
760, 29
.9) (
mmHg, in . Hg
)
(low
altitude) -Atmospheric
pressure
, Low
altitude
)
OHP 58
-RELEVANT
SIGNA
L
• High-altitude
compensation (HAC
)
FUEL CUT-OF
F
a
. Fuel Cut-Off during Deceleratio
n
During deceleration from a high engine speed
with the throttle valve completely closed (idle
contact on), the ECU halts injection of fuel in
order to improve fuel economy and reduce
undesirable emissions
.
When the engine speed falls below a
predetermined level or the throttle valve is
opened (idle contact off), fuel injection is
resumed
.
The fuel cut-off engine speed and the fuel
injection resumption engine speed are high
when the coolant temperature is low
. There are
also some engine models in which these engine
speeds drop during braking (i
.e
., when the stop
lamp switch is on)
.
2,000
Low
-
Coolant temperature
-
High
OHP 5
8
78
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