OTHER CONTROL SYSTEMS
- AS Control System, Al Control Syste
m
AS (AIR SUCTION) CONTROL
SYSTE
M
The AS system is operated by the ECU when
exhaust emissions tend to increase
; e
.g
., when
the engine is cold and during deceleration
.
Under other operating conditions, this system
does not operate to prevent overheating of the
TWC (three-way catalyst)
.
4
Al
(AIR INJECTION) CONTROL
SYSTE
M
The Al
system is operated
by the ECU when
exhaust emissions tend to increase
; e
.g
., when
the engine is cold and during deceleration
.
Under other conditions, this system does not
operate to prevent overheating
of the TWC
.
OPERATION
*
OPERATION
*
The ECU switches on the VSV for the AS system
and operates the AS system when all of the
following conditions are met
:
a
. Engine col
d
• Coolant temperature below 35°C (95°F)
•
ER
power enrichment not operating
.
• Engine speed below a predetermined level
.
b
. Deceleratio
n
• Coolant temperature above 35°C (95°F
)
• IDL contact closed (accelerator pedal com-
pletely released
.
)
• Engine speed between about 1000 and 3000
rpm
.
* Depending on the engine models
.
VSV
Reed valv
e
r
VSV
OHP 9
1
From air cleane
r
AS valve
When it is activated by the ECU, the VSV
introduces intake manifold vacuum into the ASV
(air switching valve) diaphragm chamber
.
This causes the air discharged by the air pump to
pass through the check valve and be injected
into the cylinder head's exhaust port
. If the
supply of current to the VSV is stopped,
atmospheric air is introduced into the ASV's
diaphragm chamber and the passage to the air
injection exhaust port is closed off, resulting in
the discharged air pushing against the spring
inside the ASV and being discharged outside
through the silencer
.
* Depending on the engine models
.
From air cleaner
129
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