2002 Saab 9-5 Owner's Manual - Page 150

150 Starting and driving WARNING If the engine is being run with the car on a rolling road or dynamometer, 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. 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. • 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. Important considerations with catalytic converters NOTE Use only unleaded gasoline. Leaded gasoline is detrimental to the catalyst and oxygen sensor and will seriously impair the function of the catalytic converter. The catalytic converter is an emission-control device incorporated in the car's exhaust system. It consists of a metal canister with a honeycomb insert, the cells of which have walls coated in a catalytic layer (mixture of precious metals). To ensure that the catalytic converter continues to function properly, and also to avoid damage to the converter and its associated components, the following points must be observed: • Have the car serviced regularly in accordance with the service program. The fuel and ignition systems are particularly important in this context. • Always be alert to any misfiring of the engine (not running on all cylinders) and any loss of power or performance. At the first sign of a malfunction, reduce speed and take the car to an authorized Saab dealer as soon as possible. • If the engine fails to start (in very cold weather or if the battery is flat), the car can be push started (manual gearbox only) or started using jumper cables to a donor 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.