1. if disable mod_security, will the issue gone?
2. you can strace the 100% CPU process, to know what it's doing when 100% CPU:
strace -p pid-of-100%-CPU-process
3.you can provide us the access to the server to watch the issue and troubleshoot on it.
>its happend every 5 min (arround)
while this is bad for a production server, it's good for debug.