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Idle speed, sometimes simply called "idle", is the rotational speed an engine runs at when the engine is idling, that is when the engine is uncoupled from the drivetrain and the throttle pedal is not depressed. In combustion engines, idle speed is generally measured in revolutions per minute (rpm) of the crankshaft.
Letting a car idle requires more time for the vehicle to warm up and allows excess fuel to get into the engine, which isn't good for wear and tear.
A cold start is an attempt to start a vehicle's engine when ambient temperatures are much lower than its normal operating temperature. [1] A cold start can be difficult for an engine due to higher viscosity of oil and fuel in cold temperatures.
Some idle management technologies are so comprehensive, they are able to manage the engine's on/off ignition while retaining control of auxiliary functions, such as vehicle climate, anti-theft, operator security, and more, even when the engine is powered off. Idle reduction can also be achieved by more efficient control of stop lights [34] and ...
The butterfly valve often contains a small "idle cutout", a hole that allows small amounts of fuel/air mixture into the engine even when the valve is fully closed, or the carburetor has a separate air bypass with its own idle jet. If the engine is operating under light or no load and low or closed throttle, there is high manifold vacuum.
An engine that runs too hot or too lean may produce an environment conducive to allowing unspent fuel to burn. An idle speed that is too fast can leave the engine with too much angular momentum upon shutdown, raising the chances that the engine can turn over and burn more fuel and lock itself into a cycle of continuous running.
The result is an engine that fails to maintain idle RPM and frequently stalls. A jammed actuator may be freed simply by cleaning it. However an actuator that has stopped working due to a fault in its servomotor will need replacement. Air leaks in either the stepper housing or pipes will cause elevated idle RPM.
Performance tuning of an engine can involve revising some of the design decisions taken during the development of the engine. Setting the idle speed, air-fuel ratio, carburetor balance, spark plug and distributor point gaps, and ignition timing were regular maintenance tasks for older engines and are the final but essential steps in setting up ...