Translation guide
The state of an engine running while the vehicle is not moving, or a person being inactive or doing nothing productive.
Describing a vehicle's engine running while stationary.
Describing a person who is not doing anything productive or is wasting time.
Literally 'being without doing anything'. A natural way to describe idling in a neutral sense.
Both mean the engine is idling. アイドリング is a loanword and sounds more technical or modern. エンジンをかけたまま is a native phrase and can be used in everyday warnings or instructions.
Please stop idling.
Please don't leave the engine idling.
Literally 'with the engine left on'. A natural way to describe idling in instructions or warnings.
Don't leave the car with the engine idling.
Refers to the automatic start-stop system that shuts off the engine when idling. Common in car specifications.
This car has an idling stop function.
He was idling all day.
Means to hang around or loaf about. Implies idling without a clear purpose, often in a leisurely way.
Stop idling during work.
Means to be lazy or neglect one's duties. Stronger than just idling; implies a lack of effort.
Can sound negative; use when idling is due to laziness.
He is always idling (being lazy).
Literally 'waste time'. Used when idling is seen as unproductive.
You're just idling (wasting time).
エンジンをかけたままにしないで。
Don't leave the engine idling.