2002 Saab 9-3 Owner's Manual - Page 149

Starting 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 performance will fall off slightly, and heavy loading should be avoided. For best performance you should use the recommended 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 perfectly 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 from losing their grip. 149 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 control system will be inoperative, and the capacity of the A/C compressor will be limited. 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.