Why is my wireless Router slowing down the speed of internet in my PC( Desktop) ?

[Aritrya]

Recently I bought a d link dir600m router http://www.flipkart.com/d-link-dir-600m-wireless-n150-home-router/p/itmdtg79yhtrykah

The problem is, Every time i connect my PC through the router, the speed slows down 40-50%. I am using a dial-up cable connection (PPPoe, Dynamic IP), no other wireless device is connected to my router ( Laptop or Mobile) . When i connect The cable to my PC directly the speed is okay. ( I coped my PC MAC ID in my router). But Strangely at night after 1.30am every day my routers speed gets perfectly fine, till 7am in morning, then again speed drops.

I contacted my ISP. He configured my router & Used my router's MAC ID ( didn't copy the PC MAC id). After that all together the whole connection got slow. His, network engineer came and connected the cable Line ( without Using my router) to his laptop & used his password & Username to log in. He got 50% slow speed from the cable itself (without the router being used ). After all this, same around 1.30am at night the speed gets okay till 6am.

I tried hard reset of the router. Re configuring. Opening ports. disabling firewall, disabling anti virus, Nothing works.
(Sorry for my English)

 

[smorizio]

try using open dns or google dns see if it your isp. google is 8.8.8.8 and 4.4.4.4.
make sure you have the newest firmware on the router. check to see if the router has guest network. if it is turn it off. one thing also has anyone from the isp check the line on the house. make sure no one tapped into it.