Abstract: A system and method for diagnosing output power of an internal combustion engine includes means for diagnosing potential causes of low engine output power or torque and means for estimating actual engine output power or torque. In a preferred embodiment of the diagnosis of engine output power, low engine output power is first investigated for authenticity to verify whether a low engine output power condition exists. If one exists, a zero fueling engine cranking test is conducted to determine whether relative compression values for each of the cylinders are within specification, and any problems associated therewith are corrected by service personnel. If the low engine output power problem is not corrected in accordance with the engine cranking test, a snap-throttle cylinder balancing test is conducted to balance the relative power contribution from each cylinder.

Abstract: A system and method for measuring individual cylinder power contribution by cutting out individual cylinders of a multi-cylinder engine and performing a snap-throttle test on the engine. Engine speed versus time data is collected and stored during each snap-throttle test. This data is then used to calculate the power contribution provided by each cylinder using various methods, such as a least squares analysis of the speed data or by an analysis of the kinetic energy of the test engine.