Methods and systems for diagnosing engine cylinders

A method for an engine having a first cylinder bank and a second cylinder bank, the banks together having a plurality of cylinders, the method comprising:

• testing each cylinder of the plurality of cylinders of the first cylinder bank and the second cylinder bank while maintaining airflow to the first and second cylinder banks substantially the same, including for each test cylinder:
• while maintaining operation of the engine within a mid-load notch engine load range and monitoring a crankcase pressure, adjusting fueling to at least one cylinder of the plurality of cylinders to increase a load on each of a plurality of remaining cylinders, the plurality of remaining cylinders including all cylinders in the plurality of cylinders excepting the at least one cylinder for which fueling is adjusted;
• and
• responsive to the crankcase pressure increasing by greater than or equal to a threshold magnitude, indicating degradation of the test cylinder.

A vehicle system, comprising:

• a first bank of cylinders and a second bank of cylinders forming a plurality of cylinders comprising a test cylinder;
• a fuel system fluidically coupled to each of the plurality of cylinders;
• a crankcase coupled to each of the plurality of cylinders;
• a pressure sensor coupled to the crankcase;
• and
• a controller communicably coupled to each of the fuel system and the pressure sensor, the controller executing instructions stored in non-transitory memory to, while maintaining horsepower via restricting an engine load of the vehicle system to a mid-load and maintaining airflow to the first and second banks substantially the same, and for each of the plurality of cylinders:
• receive a first output from the pressure sensor prior to adjusting fueling to the test cylinder of the plurality of cylinders, the first output indicating a first crankcase pressure with all cylinders operating;
• adjust fueling from the fuel system to the test cylinder;
• receive a second output from the pressure sensor following adjusting fueling from the fuel system to the test cylinder, the second output indicating a second crankcase pressure;
• determine a difference between the first and second crankcase pressures;
• and
• responsive to the difference being greater than a threshold difference, indicate degradation of at least one cylinder of the plurality of cylinders, wherein operation alternates between all cylinders operating and with the test cylinder fueling adjusted, yet with horsepower maintained and airflow to the cylinder banks maintained substantially the same, and further with engine speed maintained substantially constant throughout said operation.