An injector-igniter assembly includes a passive prechamber and a fuel injector. In an internal combustion engine, fuel is directly injected into a combustion chamber to mix with air in the combustion chamber. Embodiments enable filing the prechamber at different air-fuel-ratio than the main chamber without directly filling the prechamber with fuel. The prechamber has jet apertures in fluid communication with the combustion chamber. In operation, fuel is injected directly into the combustion chamber though nozzles to form a cloud adjacent to openings into the prechamber. Subsequently, mixed fuel and air is ingested into the prechamber from the combustion chamber and ignited. The degree of mixing prior to ingestion into the prechamber can be controlled using different nozzles configurations. Ignited gaseous fuel and air is expelled from the prechamber through the jet apertures and into the combustion chamber as a flaming jet with a core of gaseous fuel.