Fiat 1998 Marea Weekend, Service Manual

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Marea-Marea Weekend
ft** Engine
99
range
Fuel system
10.
Starting
During starting, it is not possible to carry out the normal management of the advance because the consid-
erable fluctuations in the rotation speed do not allow the correct calculation of the dwell and the advance.
The control unit implements a fixed advance for the entire time the engine is driven by the starter motor.
Operation at high temperatures
The strategy is enabled when the temperature of the intake air exceeds a certain level.
The "basic" advance value is reduced according to this temperature.
Operation in cut off conditions
The injection advance is reduced on entry into cut-off conditions: from the moment the fuel supply is re-
stored, the advance is gradually returned to the "basic" value.
Operation in take-off conditions
This strategy reduces the advance when the vehicle sets off from stationary.
Operation with the engine idling
When the engine is idling, the management of
the advance is implemented independently of
the "basic" advance.
The idle advance is correctly in a manner in-
versely proportional to the variation in the
speed in relation to the pre-set speed, in turn,
dependent on the temperature of the coolant.
In particular, the advance is increased if the
speed decreases and descreases if the speed
increases in order to guarantee the stability of
the actual speed.
4F011PJ01
A a: idle ignition advance correction
+ARPM: idle speed above the nominal value
-ARPM: idle speed below the nominal value
Control of the detonation
This strategy has the task of detecting the presence of detonation, by processing the signal coming from
the sensor. The strategy continuously compares the signal coming from the sensor with a level which is, in
turn, continuously updated to take into account background noise and the ageing of the engine.
If the system recognizes the presence of detonation, the strategy reduces the ignition advance, proceeding
in steps of 3° up to a maximum of 9° until the phenomenon has disappeared. Later, the advance is gradu-
ally restored to the basic value or until the phenomenon starts again.
The strategy also has a self-adjustment function which memorizes the reductions in the advance which are
continuously repeated, adapting the advance to the different conditions in which the engine finds itself
(for example, the use of a low octane rating fuel). The strategy is capable of restoring the advance to the
value memorized if the conditions which caused the reduction disappear.
Copyright by Fiat Auto
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