Method of adjusting idle spark for an individual cylinder of an internal combustion engine

A method of adjusting idle spark for an individual cylinder of an internal combustion engine comprising the steps of:

• calculating a crankshaft acceleration for the individual cylinder;
• calculating an average crankshaft acceleration for the individual cylinder based on the calculated crankshaft acceleration;
• multiplying the calculated average crankshaft acceleration by a proportional constant to obtain an average acceleration error for the individual cylinder;
• summing a product, an integral and a derivative of the average acceleration error for the individual cylinder to obtain an adaptive spark advance;
• determining a new spark advance for the individual cylinder by summing the adaptive spark advance with a nominal spark advance;
• and
• adjusting idle spark for the individual cylinder using the new spark advance for the individual cylinder.

A method of adjusting idle spark for an individual cylinder of an internal combustion engine in an automotive vehicle, said method comprising the steps of:

• determining whether at least one predetermined condition is met for an individual cylinder;
• ending the method if the at least one predetermined condition is not met for the individual cylinder;
• subtracting a previous engine speed from a current engine speed and dividing by a time period to obtain a crankshaft acceleration for the individual cylinder if the at least one predetermined condition is met for the individual cylinder;
• multiplying a current crankshaft acceleration for the individual cylinder by a predetermined average rate constant to obtain a first product;
• multiplying a previous average acceleration for the individual cylinder by one minus the average rate constant to obtain a second product;
• adding the first product to the second product to obtain an average crankshaft acceleration for the individual cylinder;
• multiplying the average crankshaft acceleration by a proportional constant to obtain an average acceleration error for the individual cylinder;
• summing a first constant multiplied by the average acceleration error with a second constant multiplied by an integral of the average acceleration error with a third constant multiplied by a derivative of the average acceleration error to obtain an adaptive spark advance for the individual cylinder;
• determining a new spark advance for the individual cylinder by summing the adaptive spark advance with a nominal spark advance;
• and
• firing a spark for the individual cylinder using the new spark advance for the individual cylinder.