Operation Manual

155Starting and driving
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 fuel with an
octane rating of AON 90. For cars with
205 hp engines and the Viggen, the
system is optimized for AON 93. One of
the advantages of the system is that it
enables the engine to be run safely on
lower-grade fuel, although not lower
than AON 87. However, engine perfor-
mance will fall off slightly, and heavy
loading should be avoided. For best
performance you should use the rec-
ommended grade of fuel, AON 90
(205 hp engine and Viggen AON 93).
• The maximum boost pressure is
adjusted automatically to the knocking
or pinging tendency of the engine.
Occasional, short-lived knocking when
the engine is under a heavy load is per-
fectly normal; the extent will depend on
the grade of fuel in the tank.
• Isolated instances of knocking are
more likely to occur with low-octane
fuel. This controlled form of knocking,
followed by a reduction in the boost
pressure, is a sign that the wastegate is
functioning and is perfectly safe for the
engine.
Saab 9-3 Viggen: The Saab 9-3 Viggen has
a high-performance engine which means
that a certain amount of care should be
exercised, in particular when accelerating in
the lower gears. This is especially important
when the road surface is slippery to avoid
the driving wheels losing their grip.
Limp-home
The car’s engine management system has
a diagnostics function that, once the engine
has been switched off, checks a number of
internal functions. If a throttle valve fault is
detected, the engine management system
will initiate limp-home mode for the valve.
This means, for example, that idling speed
regulation will be impaired, the cruise con-
trol system will be inoperative, and the
capacity of the A/C compressor will be lim-
ited.
When starting the car in limp-home mode at
temperatures below 32°F (0°C), depress
the accelerator slightly.
If the diagnosis function detects any faults in
the engine management system, the
“Engine malfunction (CHECK ENGINE)
“ indicator in the main instrument panel
will light up (see page 63). The car should
be checked as soon as possible at an
authorized Saab dealer.
NOTE
If constant knocking occurs every time a
load is put on the engine, this indicates a
malfunction in the system.
Have the car checked without delay by an
authorized Saab dealer.
NOTE
If the engine is being run with the car on a
rolling road or dynamometer, longer than
for a standard state emission inspection,
to ensure adequate cooling, air must be
blown into the engine compartment and
under the car at a rate equivalent to the
ram-air effect that would be obtained at
the corresponding road speed.