The invention relates to an internal combustion engine comprising a set of combustion chambers, each combustion chamber (2) being provided with a controllable intake valve (7) configured for opening and closing an intake port (8), a controllable exhaust valve (9) configured for opening and closing an exhaust port (10), a piston (5) displaceable back and forth in said combustion chamber (2) between a top dead center (TDC) and a bottom dead center (BDC), and a fuel injector (16). The internal combustion engine (1) further comprising an intake manifold (12) connected to the intake port (8) of each combustion chamber of said set of combustion chambers. The internal combustion engine (1) is configured to be operated in a catalytic converter warm-up mode, wherein each combustion chamber (2) is configured to be driven in four-stroke operation comprising a 720 crank angle degrees cycle, and is configured to open the intake port (8), the intake port (8) starting to open in the range 90 to 180 CAD, and close the intake port (8), the intake port (8) becomes fully closed in the range 180 to 270 CAD, open the exhaust port (10) during the power stroke, the exhaust port (10) starting to open in the range 405 to 495 CAD, open the intake port (8) during the exhaust stroke, the intake port (8) starting to open in the range 610 to 690 CAD, and close the exhaust port (10) during the exhaust stroke, the exhaust port (10) becomes fully closed in the range 630 to 710 CAD, wherein the exhaust gas is forced into the intake manifold (12) by means of the piston (5), mix fuel and exhaust gas in the intake manifold (12), and close the intake port (8), the intake port (8) becomes fully closed in the range 700 to 720+20 CAD.