Motherboard help please!

So originally I had a Asus P8Z77-V along with a i5-2500k. My original problem was that I was getting more and more false starts. It went from every 1 in 10 times starting the pc, to every single time. I went ahead and upgraded my pc to a Asus Sabertooth Z97 Mark II with a i5 4690k. I even bought a new Evga 750g2 power supply to go with it.

I have everything plugged in and for the most part everything works fine except for a few small problems. Firstly, I dont get false starts anymore (woo hoo!) but every so often my pc will either freeze at the bios flash screen or I will get a 2 or 3 round boot loop. When it freezes at the bios flash screen I have to completely unplug my power supply for about 5 minutes and then it will boot up. When its frozen I cant even access the bios. Also when it freezes the boot_device led stays on.

Secondly, I have two fans that have the 3 pin connector. I have those connected directly to the motherboard headers. They turn on and work fine, however when I shut my pc down everything shuts down besides those 2 fans. I have two fans with a 4 pin connector and those shut down just fine. Even the LAN port in the back still has lights on after the pc is off. Its like my motherboard is still receiving power after being shut down.

So what have I done to try and fix this? I have first reset the cmos by taking the battery out and resetting the jumper. Still doesnt work. I have swapped out my ram and ran a 10 hour memtest86 and have come up with 0 errors. I made sure my SSD with windows was plugged into the first sata port and made it first in the boot order. All my drives pass the SMART test and have scanned for bad sectors. The only thing that worked was plugging those 2 fans with the 3 pin connectors into a molex adapter thats plugged directly into my power supply. When my pc shuts down those fans do too

So my hunch tells me I have a slightly defected motherboard. Does this sound about right? Just would like some feedback please. Sorry for this being so long :/

Well since you changed out the Motherboard, CPU and PSU, perhaps your problem lies with your RAM, or perhaps your case has somewhere it is touching the motherboard and causing a short.

See I thought it might be the ram too, which is why I swapped it with my wifes ram. Once it started doing that with her ram too, then I ran the memtest. It went through 5 passes with 0 errors. And there shouldnt be any shorts, My motherboard is on standoffs. Thanks for the super fast reply!

Perhaps your storage device is failing?

Try a uefi update.  Test anything that the two systems had in common.

I would update BIOS/UEFI first and check settings. Certainly check RAM settings, maybe lower timing, raise voltage and see if that changes anything. Check motherboard manual about power settings etc. I've had RAM that passed memtest fine but would cause instability issues in windows. You can try force SMT when you run memtest86+, hit F2 when it starts I believe. It stresses the IMC and RAM more, though it is kinda experimental. I've had stuff just straight up freeze when I've tried F2. I've also had RAM test fine and then fail miserably when I force SMT.

I would also try to test with as little as possible connected to the MB, only CPU, one stick of RAM (in the recommended slot), all fans running directly form PSU etc. Test it a couple of time with no HDD/SDD attached etc.

That sound like mighty fine PSU, but if you can change it out and test if the issue is still there.

A thing I saw recently was that a fingerprint on the back of the CPU can cause connection problems with the socket and strange issues might appear. Might be something to check when you have checked everything else.

do you use case usb ports? if so, check those for bendend pins aswell. or just disconnect them from the board.

If you still have freezes, then i would recommend to take out the GPU, and run the computer on the igpu, and check if that solves the issue. just to determine if it might a gpu problem.

If you still have the same issues on the igpu. then it could be a ram related issue, or a drive issue maybe.

Actually the very first thing I did when I got the motherboard in my case was the bios flash. So it already is at the latest version. And I did try different ram sticks too, I used my wifes but they did the same thing. However what I did notice with this motherboard is that in the instruction booklet, it recommends using dimm slots A2 and B2 instead of A1 and B1. But that didnt help neither.

I dont believe that my SSD is failing in Samsung Magician it passes the smart test and says its still in good condition. 

How confident are you that the socket has no bent pins?

Also check that all the connections on the power cables arent sitting too far back in the connector - ie it wont make proper contact with boards power socket. Common for the 8pin if it has to really stretch itself up behind some cases motherboard plates.

Could even be that the 5v rail on your psu is a little dodgy ~ odd boot loops etc. Try with another psu if you can.

Yeah I was thinking it could be my new power supply but thats the thing I dont get. Plugging the fans into the motherboard they will still be on after I power down my pc, but when they are plugged into the psu they shut down just fine. I got an rma for both parts from amazon so hopefully Ill find out a more definitive answer.

Im pretty sure there was no bent pins the cpu slid right in no problem

try changing out the HD? sometimes when a computer boots up and tries to intialized the HD's, if one is faulty i can cause the system to hang, and if it hangs too long the system will try to reboot. give it a shot. you can test it with the HD disconnect it'll just say no boot media. or use a small linux distro on a USB drive

Did you do a fresh install on your new PC or just straight swap HDD's?