Skoda Octavia Workshop Manual page 150

24
------------ 24-42.4 ------------
Fuel Formation / Fuel Injection
In view of the steep voltage jump, the lambda
control is not able to maintain constant the ideal
mixture composition which corresponds to λ =
1.0.
A so-called reference voltage of approx. 0.4...0.5
V is programmed in the engine control unit for
analysing the signal from the lambda probe. The
control constantly fluctuates back and forward
between the „slightly too lean“ and „slightly too
rich“ states.
The control cycle should be performed at least
30 times a minute when the engine is idling at
normal operating temperature.
If there is no change to the voltage, or only a
sluggish change, the following faults may exist:
♦ Slots or holes in probe head blocked.
♦ The ventilation hole at the probe -area of
connection cable- is sealed off.
♦ Probe has been subjected to excessive ther-
mal stresses.
♦ The probe has been damaged by fuel con-
taining lead.
♦ Contact resistance in the signal wire.
♦ Probe too cold, probe heater not operating.
♦ Lambda control switched off (engine control
unit has detected fault at fuel injection sys-
tem ⇒ Interrogating fault memory and also
Reading measured value block, display
group 021).
♦ Probe damaged by contact spray or similar
products. (Because of the thermal fluctua-
tions and capillary effect, the contact spray
is drawn in through the fine cavities in the
electric cables into the probe).
♦ Probe damaged by silicone vapours. (Use
of sealants containing silicone has resulted
in traces of silicone elements being inducted
by the engine. These silicone elements are
not combusted and damage the lambda
probe).
♦ The probe has been damaged by oil ele-
ments escaping at the crankcase ventilation
or by leaks in the engine.
OCTAVIA
Edition 03.98
S00.5107.52.20