You may have a lose carbi and it would be sucking too much air and the mixture would be wrong.
A lot of times the grinding sound that is heard when going over bumps is actually the car scraping the cement. If it is not a serious problem then the best thing to do would be to drive slow over the bumps.
bad shocks or struts
Both ends
If its a ka thunk sound even on small bumps,Its most likely your STRUT MOUNTS.
Little rubber parts that help to cushion a car's suspension system, if they wear out you can hear a knocking noise when going over bumps.
Possably the struts!!!!
It maybe your suspension that squeaks when ever you go over the speed bumps.
If your vehicle is squeaking when it goes over bumps, you may need new shocks or struts. The front end of the car wears more quickly than the rear, so the issue usually begins in the front.
It is posable to have bad ball joints. Get it checked IMMIDIATLY!
Defective rear shocks. Loose exhaust components.
There are many reasons why a car would make noises going over bumps. You need to be more specific about what kind of noise? Rattling? Maybe a loose component under the car, or heat protection plates not mounted properly. If its a knocking it could be your shocks, or cv joints. There are too many possibilities that it could be. Please be more specific.
If the struts are bad on any vehicle, including the Kia Optima, the automobile is going be very bouncy going down the road. The car will start to bounce and it will seem like it is never going to stop bouncing, even with the tiniest of bumps. It might also squeak when going over bumps.