2011 gmc terrain 2.4L engine running rough

Sometimes when we stop at a stop light, the engine rpms start to go up and down. Causing the the Terrain to buck but won't throw codes or die. It will do it most of the time but its also been knowing to be perfectly fine. We have to either press on the gas just slightly or put it in park. I've had issues with the oil consumption. Had to have it done multiple times. Still hasn't helped any. (Every 2000 miles I change the oil) I've replaced the plugs, throttle body, intake tube on the air cleaner. Fuel system cleaner. Engine flushed. Changed the variable valve timing solenoids.