Abstract: To improve the idle economic performance of a gasoline engine,this paper experimentally investigats the effects of hydrogen addition fraction,cylinder cutoff,lean combustion and reducing idle speed on the engine fuel energy consumption at idle.The experiment was carried out on a four-cylinder gasoline engine equipped with an electronically controlled hydrogen port injection system.In the experiment,the cylinder closure was realized by stopping the fuel supply to the specified cylinders.Resultsshow that increasing the hydrogen volume fraction in the intake,cylinder cutoff and reducing the idle speed are all capable of enhancing the engine economic performance at idle.Among all tested methods,the combination of hydrogen addition and cylinder closure is the most effective in decreasing the engine idle fuel energy consumption.At a hydrogen volume fraction in the intake of 6.63% and two-cylinder cutoff mode,the engine fuel energy consumption is reduced by 40.07%,compared with that of the original engine.However,because of the prolonged combustion duration,the application of lean combustion is not able to further decrease the fuel energy consumption of a hydrogen-blended gasoline engine at idle.