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144 Starting and driving
Important
considerations for
driving
1 Starting and driving
• Do not use full throttle until the engine
is warm, so as to avoid unnecessary
wear. If the needle of the turbo gauge
repeatedly enters the red zone, the
engine may suddenly lose power, due
to the initiation of a monitoring system
that limits the boost pressure. Contact
a Saab dealer as soon as possible.
• Under certain barometric conditions
(high outside temperature and/or high
altitude) the needle may enter the first
part of the red zone without necessarily
indicating that a fault has arisen.
• A protective function (interruption of the
fuel supply) limits the engine speed.
2 Stopping the engine
• Do not rev the engine immediately
before switching it off - stop the engine
when it is idling.
3 Regulating the charging pressure
• The system is optimized for AON 90.
One of the advantages of boost pres-
sure regulation is that the engine can
also be run safely on gasoline with a
lower octane rating, although not lower
than AON 87. Severe engine damage
will occur if gasoline lower than 87
octane is used. However, engine
performance will fall slightly and heavy
loading and laboring should be
avoided. For optimum performance,
use the recommended grade of fuel.
• The maximum boost pressure is regu-
lated according to the tendency of the
engine to knock. Short-lived knocking
is perfectly normal. This can occur
when the engine is running at about
3,000 rpm under a heavy load. The
extent of this knocking will depend on
the grade of fuel in the tank.
• Isolated instances of knocking can
occur with low-octane fuel. This
controlled form of knocking, followed
by a reduction in the boost pressure, is
a sign that the control system is work-
ing normally, and is perfectly safe for
the engine.
Limp-home
The engine management system has a
diagnostic feature that checks a number of
internal functions. If a fault is detected in the
throttle valve, the engine management
system will set the throttle system to the
limp-home mode. This means:
• idling control will be poor (uneven idling
since regulated by ignition and fuel
supply)
• engine performance will be reduced
• the cruise control will not function
• the capacity of the A/C compressor will be
limited.
NOTICE
• If the engine sounds strange there is a
malfunction. Contact a Saab dealer
immediately.
• The use of fuel with too low an octane
rating can cause serious engine
damage.