firing on all four cylinders
firing on all cylinders = firing on all four cylinders
working or functioning at a peak level
This expression is a metaphor from an internal-combustion engine. A cylinder is said to be firing when the fuel inside it is ignited.
1998 - Entertainment Weekly - Even when his imagination isn't firing on all cylinders, Amis is still worth picking up, if only to enjoy the jazzy rhythm of his prose.
firing on all four cylinders :
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