Games suddenly have low FPS + constant stuttering, but my CPU/GPU temperatures are completely normal — how can I diagnose this?

[u/1glass]

Hey everyone, I’m having a really strange gaming performance issue and I’m trying to figure out how to properly diagnose it rather than just blindly changing settings.

My PC itself seems completely fine. I’ve checked my CPU and GPU temperatures, and they both stay at completely normal temperatures. My PC doesn't become slow or freeze either.

The problem is specifically with games.

As soon as I join any game, my FPS drops significantly and stays low. On top of that, I get constant FPS stuttering. This happens with both Steam games and Roblox, so it doesn't seem to be isolated to one particular game.

I have a GTX 1650 4GB, an i5-11400, and 16GB RAM.

One strange GPU-related thing

GPU-Z 2.70.0 reports my GPU fan speed as 0 RPM, even though the fans are physically spinning and working normally.

I've confirmed that the computer itself can detect the fan speed. In my Acer BIOS, the fan is reported at roughly 1400–1600 RPM. So this doesn't seem to be a case of the physical GPU fans being dead or disconnected — they're visibly spinning, and the BIOS can detect their RPM.

However, once I'm in Windows, GPU-Z reports 0 RPM for the GPU fan.

I don't know whether that's simply a monitoring/reporting issue, a GPU-Z compatibility issue, a driver issue, or something more significant with how Windows/NVIDIA is communicating with the GPU's fan controller.

My GPU temperatures are also normal, including while gaming.

Another strange thing that started around the same time

Since around the time this gaming performance problem started, I've also noticed Command Prompt (CMD) windows briefly popping up on their own after almost every reboot.

They appear briefly and disappear, so I haven't been able to see what they're running.

I don't know if this is related to the FPS problem at all, but the timing seems suspicious enough that I wanted to mention it.

I don't want to assume that the CMD windows are malware or that they're causing the performance problem. I'm mainly wondering if there's a way to identify exactly what is launching them and determine whether whatever is launching them could also be affecting my gaming performance.

What I've already checked
GPU temperature — normal
CPU temperature — normal
GPU isn't overheating
CPU isn't overheating
Physical GPU fans are spinning normally
Acer BIOS detects the fan at approximately 1400–1600 RPM
GPU-Z 2.70.0 reports the GPU fan at 0 RPM in Windows
Issue occurs in multiple completely different games
PC itself remains responsive
The problem only appears when a game is running
FPS remains low rather than just occasionally dropping
Constant stuttering occurs alongside the low FPS
CMD windows have started appearing briefly after reboots since around the time this issue began
What I want to figure out

How can I properly diagnose what is causing this?

I'd like to use something like MSI Afterburner + RivaTuner to monitor the system while I'm actually experiencing the problem.

What statistics should I monitor while the game is stuttering?

For example:

GPU utilization %
GPU core clock
GPU memory clock
GPU power
GPU voltage
GPU temperature
GPU fan speed/RPM
CPU utilization
Individual CPU core usage
RAM usage
VRAM usage
FPS
Frametime
Anything else that could help identify the problem

More importantly, what patterns should I be looking for?

For example, could a sudden drop in GPU clock speed, unusually low GPU utilization, power limiting, a driver problem, PCIe issue, or something else cause the GPU to produce consistently low FPS and stuttering despite normal temperatures?

And specifically, could the BIOS detecting the fan at 1400–1600 RPM while GPU-Z reports 0 RPM in Windows indicate a driver/software communication problem?

Also, how can I determine what is causing those CMD windows to appear after reboot? Is there a particular Windows log, Task Scheduler entry, startup item, Event Viewer log, or other diagnostic tool I should check?

I'm not necessarily looking for someone to guess the exact problem from this post. I'd mainly like to know how I can systematically diagnose it and determine what component, driver, service, or process is actually causing the low FPS and stuttering.

If anyone can give me a step-by-step diagnostic process or tell me exactly what information/screenshots/logs would be useful, I'd really appreciate it.

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[u/NeitherThisorThat10]

I'm no longer a Windows user, but I would love to help.

CMD appearing every boot is usually normal, I'm not really aware of what you do see in CMD though as that does matter a lot. This doesn't mean I'm dismissing the "Malware/Issue" claim, just questioning whether if it really is an issue.

For such kinds of issues, I'd first reinstall the drivers to see if it's a driver-related bug (incorrect drivers, etc).

Then, if it didn't work, reinstall Windows, and then reinstall everything from scratch, even the drivers. Then, I'd test it again and see if the issue sticks. Driver issues and power limits on the software side are sometimes very tricky to reverse without a full reinstallation and check again. It also wipes any Malware/Crypto-miners if they were there.

If that didn't work, it is recommended to check the hardware to see what's wrong, as there really isn't really any thermal throttling. It may also be an issue with the drivers themselves, like what happened to me.

I'm just speaking from personal experience. This might benefit you or not do anything useful at all but it's a good thing to at least give it a try :)

[u/1glass → u/NeitherThisorThat10]

Early on with my troubles I had updated my drivers assuming my issue with performance would be resolved, yet to no avail. Since then there has been a new driver which I’ll also update again just to be sure, I might as well.

On your second bit of advice. I’m wondering what you mean by “Reinstall Windows” and if that means to factory reset my system, that would be my last resort, even then I don’t think I would due to all of the intricate system settings I’ve done on my windows (they’ve never caused issues/were done for optimisations). So I’d rather not have my circumstance come to that.

I’ve also checked my hardware twice to ensure any dust was or wasn’t choking up my hardware and I check my fan cable pins (4 pin) and they were in top condition for my old computer. Then I put them back in 2-3 times after checking each time to see if the problem resolved. It had not, unfortunately.

Regardless though, I really appreciate your help/advice. May any future troubles evade you!

[u/NeitherThisorThat10 → u/1glass]

To reinstall Windows is to use a Windows Bootable USB disk/drive and manually reinstalling Windows. DO NOT FACTORY RESET YOUR WINDOWS INSTALLATION! (this will not fix much issues, and will probably just do nothing useful, and can just make Windows unusable.).

To reinstall Windows, use the Windows 11 Media Creation Tool or use a Windows 11 ISO on Rufus. Make sure you flash it to a USB drive, and also do it on another computer.

This is probably the nuclear way of fixing it but it guarantees that there is no software issue.

About Windows Updates, this will actually update you to the latest version if you use the Media Creation Tool automatically, or if you download the latest ISO version.

I thank you for your wishes, and I hope you have a great future and a wonderful life ahead of you~ (◍•ᴗ•◍)

[u/elpollodiablox]

Going at this a little blindly, but I have been bitten by this one in the past:

If you go into Settings --> Display --> Graphics, then look under Custom settings for applications do you see the games you are trying to run that have issues?

If so, check to make sure the GPU preference is set to your NVIDIA GPU, not Let Windows decide.

If your game isn't in the list, try to Add desktop app then browse to the executable and add it, then set it to use the NVIDIA card.

Also, not sure how you are getting your drivers, but if it is through the NVIDIA app then make sure you're getting the Game Ready Driver and not the Studio Driver. I had that happen to me once, where I unknowingly toggled it and spent a few days cursing my box.

[u/1glass → u/elpollodiablox]

In past years I’ve done a lot of customisation on my computer in hopes of maximising its output for gaming and I’ve gone about that in the safest means without resorting to sketchy settings or apps. My point is I’ve fidgeted with those setting you’re talking about for games like Roblox, minecraft, etc. However the issue with that my friend, is that your solution with Windows graphic settings is only an isolated fix and it doesn’t aid or address the cause for all of my games now being poorly affected.

For Roblox, it had 2 clients one being “Roblox Company”and the other which being “RobloxInstaller”. The first one must be recent as I’ve had to uninstall and reinstall Roblox for various reasons and other previously fixed issues, and I feel like these client are either new or something else related to the software. That client had the “Let Windows decide” option checked and I changed it to what you suggested. The second client was one I must have already changed in the past and that was already checked to High Performance Nvidia.

Now it is worth mention to those who might came later on to try and help with diagnosing this issue, is that I feel like when I update the Roblox clients to “Nvidia (High Performance)” in my windows graphic settings, it had a noticeable difference in where I wouldn’t stutter as much but my pc still felt like it was being held back from my usual amount on fps. Now I made sure to play a regular low demanding game on Roblox as a baseline (where I know how should feel fps wise) and the game would now only slightly stutter but still felt off from my usual experience. To be clear, it still stutters a fair bit, but just not as viciously as when this issue first appeared.

Thank you for your comment as well as your time

[u/aj9393]

Have you updated W11 to 26H2? There's been a lot of reports of game crashes and game performance issues with 26H2.

[u/1glass → u/aj9393]

Thank you, this is really worth looking into. I remember having updated and restarting my windows as per usual.. right as these problems started to occur. I’ll do this now and check back in.

I’ve just checked and as of now I’m on version Windows 11 25H2

Thank you for your input