Idle running

Idle running is operating an engine at its lowest stable no-load speed, holding it ready to take load without stalling. On a propulsion two-stroke it is the dead-slow setting used during maneuvering; on a generator diesel it is a warm-up or standby state before the breaker closes. Prolonged idling on residual fuel causes problems: incomplete combustion fouls the turbocharger and exhaust trunk with soot, cylinder and exhaust temperatures fall, and unburned fuel and cold corrosion attack the liner. Makers limit continuous low-load and idle hours and call for periodic load-up. Auxiliary engines on distillate idle more cleanly than two-strokes on heavy fuel.