Low load operating point for a controlled auto-ignition four-stroke internal combustion engine is reduced without compromising combustion stability through a valve control operative to establish sub-atmospheric pressure conditions within the combustion chamber into which fuel and exhaust gases are introduced. A split-injection control operative to introduce a first fuel fraction into the combustion chamber during an intake stroke and a second fuel fraction into the combustion chamber during a compression event, in combination with the valve control, provides further reductions in low load operating points without compromising combustion stability.