My 02 kia spectra GS makes a rattling sound when it starts up

Could be a number of thing,s ,bad lifter,s,to a bad idler pully,if sound stay,s all the time,it may be bad teitioner ether timing belt pully,or drive belt pully,you have to narrow it down to location to know for sure.

I'm having the same issue. I have eliminated all front accessories by removing all belts. I have removed the valve cover and inspected the cams, and lifters which all look fine. I have pulled a compression check which passes. I have replaced the timing belt. Tensioners are serviceable. If you take a wrench and tap on the valve cover the sound you hear is identical to what sound I hear when it's running but very rapid, no way I could tap it that fast by hand but it's the sound that matches. When asking others to pinpoint the sound the consensus is top of motor center aft. Again, with cover removed I find zero contact points. I'm completely baffled. Any ideas?

Sounds like a bad hydraulic lifter.......