What do make the knocking noise in the engine when you give gas? on 1999 Buick Century

What do make the knocking noise in the engine when you give gas?
all the fluids are full.It only make the noise when gas is giving. Doesn't matter what gear you are in.

3 answers
Timming gears....going bad need replaced..
To many possibilities, a mechanic really needs to hear this noise to be able to make a diagnosis.
Have it checked by a knowledgeable person that can hear what kind of noise it is. It may even be an octane ping that sounds like a knock to you. May not be the engine, but maybe the gas you are using. Just a thought.