1998 Land Rover Discovery 2 Hi Drive Landrover Will Start First Time Every

Hi, when I drive my landrover it will start first time every time, but some time it will stop revving it will still idle fine but when I press on the accelarator it won't do a thing. After between 10-40 seconds it will be fine again. When it does stop revving the check engine light comes on. I have changed the fuel filters.