Internet connection slows down drastically after turning on PC

[Wetarek]

Hey guys!
Yesterday I encountered really strange problem. About 30 minutes after turning my PC on my Internet connection slowed down significantly (to the level that didn't allow to use it in any way). The ony way to fix it was by restarting a modem and, after it had restarted, restarting router (restarting modem and router at the same time didn't give any results). But as long as the PC was turned on and connected to router, the Internet connection slowed down eventually. I was able to maintain normal Internet speed only by keeping the PC shut down or by unplugging it from the router. I checked if there are no viruses on my PC, but it was clean.
Do you guys have any idea how to fix this issue?
Both my mobo's and router's drivers are up to date, although the router is using beta version.

PC specs :
1. GPU - Gigabyte GTX 970 G1 Gaming
2. CPU - Intel Core i5 2500K @ 4.5 GHz
3. MoBo - Asus P8Z68-V Pro
4. RAM - HyperX Predator 2x4 GB @ 1600 MHz
5. CPU cooler - SilentiumPC Grandis XE1236 v2
6. SSD (system drive) - HyperX 3K 240 GB
7. HDD - WD Black 500 GB
8. PSU - XFX XTR 650W

OS - Windows 7 64 bit SP1

Router - TP-Link WR841N (connected to PC via ethernet cable)

Modem - Cisco EPC 3008

 

[Ralston18]

No noted error messages, warnings, or yellow exclamation marks anywhere.

Any errors or warnings in the Event Viewer logs?

Are you using a built in motherboard LAN port or a third party adapter? If the latter is the LAN card USB or PCIx? Make/model?

Easiest to try is to run the network troubleshooter and see what it finds and can do.

Then, other options:

First try connecting the PC to a different router port.

Second, try another known working ethernet cable.

Third, check your network adapter's configuration and settings. Check that you have current manufacturer's drivers for your LAN adapter.

If applicable, i.e., third party adapter, pull and reinstall the network adapter.

Watch for any error messages or warnings throughout all that you do.

 

[Wetarek]

No noted error messages, warnings, or yellow exclamation marks anywhere.

Any errors or warnings in the Event Viewer logs?

Are you using a built in motherboard LAN port or a third party adapter? If the latter is the LAN card USB or PCIx? Make/model?

Easiest to try is to run the network troubleshooter and see what it finds and can do.

Then, other options:

First try connecting the PC to a different router port.

Second, try another known working ethernet cable.

Third, check your network adapter's configuration and settings. Check that you have current manufacturer's drivers for your LAN adapter.

If applicable, i.e., third party adapter, pull and reinstall the network adapter.

Watch for any error messages or warnings throughout all that you do.

1. No error messages whatsoever;
2. There are no "Critical" logs, a few "Error" (ID 102, 1002, 7001, 7023, 8193, 10001 and 36887 - I have no idea what they mean) and 1 "Warning" (ID 1014);
3. I'm using built-in motherboard LAN port;
4. Troubleshooter didn't find any errors;

I also found out that if i plug in an ethernet cable connecting my PC and router when the PC is already running, there are no problems with my Internet connection, it works absolutely fine. What does it mean?

 

[Kewlx25]

What's your network usage? Maybe you installed some software that's using all of your bandwidth and it just takes a while for it to get up to speed.

 

[Ralston18]

The Warning ID 1014 is helpful - indicates a DNS related problem.

I randomly googled a couple of the other errors and there is a bit of a pattern. Unfortunately there also many unrelated hits that are just attempts to sell you some "we can fix it" software no matter what Error ID is searched on. Other "solutions" got really involved and I obviously do not know enough about your computer and network to even suggest one of those. If you do the searches you might spot something relevant to your situation that, for the moment, may seem unrelated to me.

Could be that when you turn on the computer it attempts to connect but other some process is getting in the way.

If you disconnect and start up the computer sees no network and continues booting up. Once running that other process is "out of way" so to speak and plugging in live launches the normal network connection process.

What I would do is clear the logs and boot from power up with the network plugged in. Watch the Event Viewer logs, and the performance/resource monitors to see what launches and runs. Again keep track of the errors and warnings.

Do that again where you plug in the cable while already running. You should see the network related process start up.

May take a couple of runs but I would expect that you would catch some difference.

And, as Kewlx25 mentioned, you may spot some software grabbing bandwidth or other resources, to the point where network connectivity is disrupted.

 

[Wetarek]

Well, the problem fixed itself - today everything seems to work just fine but I'll have to take a deeper look into those errors and warnings in Event Viewer.