Subaru 2002 Impreza Service Manual page 53

AIR LINE
Fuel Injection (Fuel System)
2. Air
Line
A: GENERAL
The air filtered by the air cleaner enters the throttle body where it is regulated in the volume by the
throttle valve and then enters the intake manifold. It is then distributed to each cylinder where the
air is mixed with fuel injected by the injector. During idling operation, air flows into the cylinder
through the idle air control solenoid valve, bypassing the throttle valve. This enables controlling
the engine idling speed properly.
B: PRESSURE SENSOR
The pressure sensor is attached to the top of the throttle body, and continuously sends to the en-
gine control module (ECM) voltage signals that are proportional to intake manifold absolute pres-
sures. The ECM controls the fuel injection and ignition timing based on the intake manifold abso-
lute pressure signals in addition to other signals from many sensors and other control modules.
Connector
B k L
Terminal
"i#
I
I
I
I
Absolute pressure
NF0318
C: THROlTLE BODY
0
In response to operation of the accelerator pedal, the throttle valve in the throttle body opens/
closes to regulate the volume of the air drawn into the combustion chamber.
0
During idling, the throttle valve is almost fully closed and the volume of air passing through the
throttle body is less than that passing through the idle air control solenoid valve.
0
More than half of the air necessary for idling is supplied to the intake manifold via the idle air
control solenoid valve which controls properly the engine idling speed, so the idling speed needs
not be adjusted.
FU-3