Strange problem with sysload...

[Zgryt]

Some of scripts is generating a sysload between 90% / 100%, i can't find it (it isn't in scripts_profiles, long_running_scripts, and it doesn't fall into runaway to) The lag is freezeing server for one minute, then for few seconds silence. That takes several minutes to 40 max. Then server have sysload between 6%-30% for few hours. Lag occures at random.
How to find it?

Server stats:
2x2,4GHz Xenon
5 GB Ram

ps. Sorry for my poor english... Its hard to say what im realy thinking