Router slows connection

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i have a linksys N router i believe its a wrt 160n. I noticed my connection was crap and pages were timing out so i went on speedtest.net and ran the test. It came out with 1.2 mb down and 1.6 mb up which is terribly slow. I did a power cycle and nothing changed. I unplugged the router and plugged directly into the desktop. I reran the test and got 28mb down and 7mb up. I hooked the router back up and now it runs at 14-18 down 4-5 up... is there something wrong with the router or its configuration? or do routers automatically reduce speeds?