Doom3world

I'm having really irritating ping problems in any server I join. It keeps constantly jumping between 30-300 making it hard to shoot targets let alone move. I have bought Quake 4 in steam and this is the first and the only game I've had this problem in. I do not download anything meanwhile nor my connection is being interrupted, the server location is ideal and nobody else in the server is having ping problems. I have no ping problems while I play in a server created by me, don't know how it is for those who join it though. Performance in the game overall is satisfying. Help would be really appreciated, because I wanna play this game!