Methods and systems are provided for monitoring torque delivery in a variable displacement engine using air flow metered via a throttle body model. During conditions when air flow estimation can be inaccurate, such as at wide open throttle, an induction ratio applied to the engine is constrained to 1.0, even if the operator torque demand is low. VDE degradation is inferred based on the commanded induction ratio relative to an actual induction ratio estimated based on the torque delivery.