WiFi acting like dialup or worse

I got a new MacBook Pro last fall and it’s worked fine until a few days ago. Suddenly my online connection started going in and out. I have an occasional minute where it seems fine, but most of the time it looks like I’m working with dial-up speeds or it won’t load web pages at all.

At first I thought it was my router going out, but my iPad and PS4 have no trouble connecting to WiFi. I thought it might be malware or other clutter on my system, so I updated security settings and upgraded from 10.9 to 10.10. Firefox ran normally for a few minutes, but soon slowed down again. Plus, I don’t have any issues when I have a hardline connection to the router. It’s not just Firefox. Other online applications run extremely slow or not at all.

Could my WiFi card have a defect that shows up 7+ months after I started using it? The system is still under warranty till October. Would that cover parts and labor to replace the WiFi card?

Have you taken it to your local McD's, Starbucks, friend's house, etc. and tried it on another network?
Have you reset the router (unplugged the power cable for 30 seconds)?
Removed the network in Network Preferences and added it back from scratch?
Removed any other misc networks it may have connected to in Network Preferences - Wifi - Advanced?

The network preferences fix seems to have worked for now. I let you know if it slows back down.

It's slow again. It might not be as bad as it was before, but it's far from normal. About every 4th or 5th page I try to load gets stuck, even if it's just a Google search. Sometimes when I wake the laptop from sleep it has trouble getting the WiFi signal at all. The name of my router is on the list with a check mark next to it, but the bars are flashing as if it found the router but is having trouble connecting. After 20-30 seconds, it finds a full strength, 4 bar signal like everything is normal, but it doesn't last long.

Resetting the router was the first thing I tried. If it was a problem with the router, than why don't I have problems with my iPad or PS4?

Have you heard any other examples of MacBook WiFi cards going bad within the first year? If that is the problem, I want to get it fixed before my warranty is up.

Again, as suggested by Moderator bobtomay, have you taken your MacBook Pro somewhere you can test it on free WiFi and not from your home system? Just because your iPad and Sony PS4 are working OK at home is not a good test. If your MacBook Pro performs poorly on other networks also, that might be an indication of a problem with your Airport card or network settings. And yes, you should have Apple look at it while it's still under warranty. And you might also think about purchasing the additional Apple Care.