1. A method for detecting misfire in an engine, the engine having a plurality of working chambers and being operated in a skip fire manner, the method comprising:assigning a window to a target firing opportunity;
attempting to fire a target working chamber during the target firing opportunity;
measuring a change in an engine parameter during the target firing opportunity;
using a multi-cylinder pressure model to help determine an expected change in the engine parameter during the target firing opportunity wherein the pressure model involves estimating pressure in a skipped working chamber, wherein the determination of the expected change in the engine parameter accounts for torque added or subtracted from the powertrain by an auxiliary power source;
based on a comparison between the expected change and the measured change, determining whether the target working chamber misfired.