A control system comprising an oxygen sensor that generates an oxygen signal based on an oxygen concentration level in an exhaust gas of an engine, a filtering module that determines a filtered signal based on the oxygen signal, and an air-fuel imbalance detection module that detects an air-fuel imbalance in the engine based on the oxygen signal and the filtered signal. A method comprising generating an oxygen signal based on an oxygen concentration level in an exhaust gas of an engine, determining a filtered signal based on the oxygen signal, and detecting an air-fuel imbalance in the engine based on the oxygen signal and the filtered signal.