Method for operating a petrol engine, in particular of a motor vehicle, and motor vehicle

A method for operating a petrol engine, comprising the steps of:

• filling a pressure tank with air and storing the air in the pressure tank;
• introducing air from the pressure tank into an exhaust tract via an air duct that is different from the exhaust tract and that fluidically connects the pressure tank and the exhaust tract through which exhaust gas from the petrol engine flows, wherein the air is introduced into the exhaust tract at a point disposed downstream of a first three-way catalytic converter disposed in the exhaust tract and upstream of a second three-way catalytic converter disposed in the exhaust tract downstream of the first three-way catalytic converter, while the petrol engine is operated with a sub-stoichiometric combustion air ratio whereby desulphurization of the second three-way catalytic converter is caused;
• detecting, by way of a temperature sensor located downstream of a valve to block and release the air duct and upstream of a supercritical throttle to introduce air taken from the pressure tank into the exhaust tract, a temperature of the air in the air duct passing from the pressure tank to the exhaust tract;
• and
• setting a quantity of air to be introduced into the exhaust tract depending on the detected temperature.