ENGINE AND EMISSION CONTROL –
Emission Control System
EGR valve
Throttle
body
EGR valve
17-13
EXHAUST GAS RECIRCULATION (EGR) SYSTEM
GENERAL INFORMATION
The exhaust gas recirculation (EGR) system lowers
the nitrogen oxide (NOx) emission level. When the
air/fuel mixture combustion temperature is high, a
large quantity of nitrogen oxides (NOx) is generated
in the combustion chamber. Therefore, this system
recirculates part of emission gas from the exhaust
port of the cylinder head to the combustion chamber
through the intake manifold to decrease the air/fuel
mixture combustion temperature, resulting in
reduction of NOx.
The EGR flow rate is controlled by the EGR valve
so as not to decrease the driveability.
OPERATION
The EGR valve is being closed and dose not
recirculate exhaust gases under one of the following
conditions. Otherwise, the EGR valve is opened
and recirculate exhaust gases.
D
The engine coolant temperature is low.
D
The engine is at idle.
D
The throttle valve is widely opened.
SYSTEM DIAGRAM
Air flow sensor
Engine coolant tem-
perature sensor
Crank angle sensor
Control
relay
Engine-ECU
Battery
Throttle body
EGR valve
(Stepper
motor)
Throttle position sensor
COMPONENT LOCATION