Hi i want to asked some questions about my Kia Rio 2009 autmatic.when i drive and trot the gasoline pedals i begin to hear a noise in the motor is like a knocking.i don't know if is the gasoline in my country ARUBA.I WENT TO MY CARDEALER Topcar in aruba they have check my kia rio but didn't get the problem about the knocking in the motor,and the said to me that the problem was the injectors and they clean them but still i hear the noice.can you tell me something about that?

If when accelerating hard in 2nd gear, you get rattling sound, that is probably pre-ignition ping.
if it goes away wnen you back off slightly, then is it probably the guality of gas.
If you can not get premium gas, you can add gas line dryer alcohol, and that will raise octane.

But it could also be a rattle from the converter heat shield.

Hard to tell without seeing the car, but poor quality or low octane gasoline can cause an engine knock under hard acceleration or heavy load. This is called preignition and can cause major engine damage. Preignition can also be caused by incorrect ignition timing.