Hyundai Getz no power to accelerate and engine is jerky, like its misfiring.

When the car is under load eg. trying to pull away from standstill there is hardly any power at all. The throttle does not seem to have any effect but works fine when the car is stationary and out of gear. Engine also seems to have a slight misfire under load. Fuel consumption is quite high recently also. Nothing shows up on any diagnostics as having failed.