Malfunction diagnosis device for engine speed controller

A malfunction diagnosis device for an engine speed controller, said device comprising:

• first air control quantity calculating means for determining a first control quantity corresponding to an amount of air to be regulated by a first air quantity adjusting valve;
• first air quantity regulating means for controlling said first air quantity adjusting valve responsive to said first control quantity;
• second air control quantity calculating means for determining a second control quantity corresponding to an amount of air to be regulated by a second air quantity adjusting valve;
• second air quantity regulating means for controlling said second air quantity adjusting valve responsive to said second control quantity;
• range determining means for determining whether at least one of said air control quantities is within a corresponding range;
• and
• malfunction determining means for, when said range determining means determines that an air control quantity corresponding to a first one of said air quantity adjusting valves is outside of its corresponding range, determining the existence of a malfunction in the other of said air quantity adjusting valves.

A method of detecting a malfunction in an engine speed control system, said method comprising the steps of:

• determining a first control quantity corresponding to an amount of air to be regulated by a first air quantity adjusting valve;
• determining a second control quantity corresponding to an amount of air to be regulated by a second air quantity adjusting valve;
• determining whether at least one of said air control quantities is within a corresponding range;
• and
• determining the existence of a malfunction in a first one of said air quantity adjusting valves when an air control quantity corresponding to the other one of said air quantity adjusting valves is outside of its corresponding range.