Lag spikes. Wireless issue?

baseless research

when playing, i'll get periodic lag spikes every 1.5 minutes or so. What happens is I'll be playing along merrily at 40-60 ping, then get a sudden spike of 999 ping. After about 5 seconds everything normalises again, and I'll be dead because some ###### marine/alien killed me. I think this has something to do with the fact that I am on a wireless network. Unfortunately it's impossible for me to create a wired connection, and unless I sneakily throw a bottle of water over the router It won't be replaced either.

Router is a Linksys WRT54G model 7, I think.