Q: very low power in 2nd gear engine knocking noise

If the knocking noise happens while you feel like the vehicle is chugging, this could be a misfire. Misfires are ore likely to happen when the engine is under a load, like during acceleration. Usually a misfire will cause the Check Engine Light it come on. I would have the diagnostic engine codes read to give clues as to what system or component needs further testing. A certified technician, like one from YourMechanic, will be able to determine the cause of your misfire.