This is a problem I have had on and off, and now its happening more often. When I start my car (ussually when its cold) it makes a wierd sounds like knocking sound until then engine warms up, then its fine...anyone have have any ideas? The knocks also speed up with the RPMs.
Uh... that sounds like lifter rapping... thats a bad thing.
First check your oil. It may be pretty low. If its not, switch to a lighter oil. It wont congeal as much in the cold and will help alleviate this problem.
The cold oil is thick and moving slowly (or there isnt enough of it) and the hydraulic lifters are collapsed.
If it STILL doesnt go away, better get to a garage.