Abstract: The invention relates to a method and system for controlling an internal combustion engine (9) in a motor vehicle having a brake booster (1), a low pressure chamber (2) of the brake booster being connected to the intake manifold (8) of the internal combustion engine (9). To ensure that the brake booster (1) functions during a forced warm up of a catalytic converter, the pressure in the brake booster (1) is monitored by pressure sensors (7a, 7b). If too high a pressure is detected, the internal combustion engine (9) is actuated by an engine control system (10) to decrease intake manifold (8) pressure, for example, by increasing the engine speed after startup. Spark retard, a measure for warming up a catalytic converter, is temporarily reduced or eliminated, if increasing engine speed is insufficient to reduce pressure.