An internal combustion engine including a combustion chamber, an intake air passage communicated with the combustion chamber, an intake valve having a thermal insulator at an air-exposure portion thereof which is opposed to the intake air passage, a fuel injector disposed within the intake air passage and operative to inject an amount of fuel toward the air-exposure portion of the intake valve at a fuel injection timing, and a controller in communication with the fuel injector. The controller is programmed to set the fuel injection timing of the fuel injector to an engine intake stroke.