At least some implementations of a method of distinguishing between two loads being driven by an engine, includes the steps of determining engine speed at defined intervals, comparing a second engine speed against a previously determined first engine speed, determining if the second engine speed fits an expected pattern of engine speeds, and counting either the number of incidents where the second engine speed does not fit the expected pattern, or the number of incidents where the second engine speed does fit the expected pattern, or some combination of these two. A method of determining if an engine is operating at least near a lean limit of its air to fuel ratio is also disclosed.