when i started up my car and was getting ready to drive away i heard a knocking on 2000 Ford Focus

sound like a rock that hits the bottom of your car but there is was not rock. What could of made that sound?

Asked by for the 2000 Ford Focus
Did it go away or still knocking? Oil level and pressure ok? Several poss. causes get mechanic to take a look!
2 more answers
ball joints or sway bar end links
Broken engine mount??? .....just one more guess.......should get it looked at. IF in doubt -tow it!