Patent ID: 7894972

Claim:
A method for operating an internal combustion engine having a plurality of cylinders and, assigned to the cylinders, injection valves which meter fuel, and having an exhaust gas tract in which is disposed an exhaust gas probe whose measured signal is characteristic of the air/fuel ratio in the respective cylinder, the method comprising the steps of: recording the measured signal at a predefined crankshaft angle in relation to a reference position of the piston of the respective cylinder and assigning the measured signal to the respective cylinder as the recorded cylinder-specific air/fuel ratio, by means of in each case a cylinder-specific lambda controller, determining a controller value for influencing the air/fuel ratio in the respective cylinder as a function of the cylinder-specific air/fuel ratio recorded for the respective cylinder and activating the injection valve assigned to the cylinder in each case as a function of the respective controller value, monitoring the controller value, if the controller value reaches a first predefined threshold value, determining a first lambda quality value which is representative of the deviation of the recorded cylinder-specific air/fuel ratios assigned to the respective cylinders, if the controller value reaches a second predefined threshold value which is representative of a more pronounced control intervention than the first threshold value, determining a second lambda quality value, and determining whether the first lambda quality value is less than the second lambda quality value, and if that is the case, detecting an unstable control behavior, and if that is not the case, detecting a stable control behavior.