D:04:10
^v
Fuel,
Emission and Exhaust System
INJECTED FUEL
QUANTITY INCREASES
RICH
MIXTURE
LOW CONTENT OF
OXYGEN
IN
EXHAUST GASES
/
LOWER CHAMBER
PRESSURE DECREASES
IN DISTRIBUTOR
/
OPEN TIME OF
FREQUENCY VALVE
LENGTHENS
"ACTION
CIRCLE"
LAMBDA CONTROL SYSTEM
\
HIGH SENSOR
\ VOLTAGE
I
\
OPEN
T
IME
OF
FREQUENCY VALVE
SHORTENS
i _
_.
i
\
/
LOW SENSOR
VOLTAGE
LOWER CHAMBER
PRESSURE INCREASES
IN DISTRIBUTOR
\
/
HIGH CONTENT OF
OXYGEN IN
EXHAUST GASES
INJECTED FUEL
QUANTITY DECREASES
LEAN
MIXTURE
Fig. 30
SYSTEM CONTROL MONITORS
The oxygen sensor needs a minimum operating
temperature to deliver a signal (approximately
300°C).
In
order to achieve driveability from start,
the ECU module sets the frequency valve on a
fixed pulse ratio until the sensor warms up. This is
also the case if the sensor fails at any time during
operation.
The fixed ratio will provide a richer fuel
mixture than normal.
The pulse ratio is controlled at another fixed value
when the engine coolant temperature is below
15°C
(59°F)
or when the engine is at wide open
throttle. These conditions are determined by a
thermal switch (Fig. 31) (1) and a full throttle micro
switch (2) (Fig. 32). The fixed pulse ratio provides a
rich fuel mixture to improve engine performance
when cold or in the full throttle position.
imi
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