New 144Hz monitor help needed!

I just bought a new LG Ultragear 144Hz 4K monitor.
All set up ok, and looks nice. Playing Forza Horizon 5 I'm getting really bad stuttering - like every time I hit an object (fences, trees etc) the FPS will drop and I get a noticeable 'jump' in the game.
I've tried G-Sync on/off, V-Sync on/off, even limiting the frame rate to 60FPS but it's still happening. (My old monitor was 60FPS and I used the same settings in the game/driver).
With the monitor frame rate set to 144, the game is hitting 100-120FPS (seems high!) and the GPU is always at 99% or more. Setting a max frame rate reduces the GPU load to around 60-70 (as it was with my old monitor) but doesn't stop the bad stuttering.

I've done a DDU, and re-installed the drivers, didn't fix anything. The game didn't do the usual 'optimizing for PC' thing it always does after a new driver install.
The monitor (model 32GR93U) is shown on Nvidia's website as validated G-Sync compatible, but the Nvidia driver says it's not validatred. The G-sync options are in the NV control panel.

Is this a monitor issue? Game problem? I played the game for 2 years on a 4K Asus 60Hz screen until it broke the other week.

I've had the monitor only one day so I need to know whether I should be returning it. It's a lovely piece of kit.

Are you using a DisplayPort cable?

I'm not a gamer, but I ran a UHD 144Hz monitor in 10 bit color with DP for a time. It must have used DCS (display stream compression).

I'm far from sure that it'd make any difference, but I've always regarded HDMI as more of a TV interface than a PC one.

bobkn said:

Are you using a DisplayPort cable?

I'm not a gamer, but I ran a UHD 144Hz monitor in 10 bit color with DP for a time. It must have used DCS (display stream compression).

I'm far from sure that it'd make any difference, but I've always regarded HDMI as more of a TV interface than a PC one.

Click to expand...

Using HDMI 2.1 cable, it's a high speed cable that was supplied with the monitor.

BrianInEngland said:

Using HDMI 2.1 cable, it's a high speed cable that was supplied with the monitor.

Click to expand...

I'd still try a DP cable, just for luck. (But then, I have a few lying around.)

I'd suggest installing the "drivers" for the monitor, but LG doesn't seem to offer any. Is the monitor properly identified in Device Manager?

bobkn said:

I'd still try a DP cable, just for luck. (But then, I have a few lying around.)

I'd suggest installing the "drivers" for the monitor, but LG doesn't seem to offer any. Is the monitor properly identified in Device Manager?

Click to expand...

Yes it's identified as LG ULTRGEAR+ in Device manager

BrianInEngland said:

Yes it's identified as LG ULTRGEAR+ in Device manager

Click to expand...

Good.

I still urge trying the DP interface, if you have a cable.

That's without any real understanding on my part.

bobkn said:

Good.

I still urge trying the DP interface, if you have a cable.

That's without any real understanding on my part.

Click to expand...

Well with the the DP cable I don't get the G-Sync validation warning. Still getting FPS drops in Forza but only at certain points, normally during Freeroam. Races seem fine so it's likely a game bug

This is weird. The monitor's refresh rate is 144, 95 or 60 with DP connected. Setting to 95 or 144 causes the problems with stuttering, even if I limit the game's max rate to 60.
Setting the monitor to 60Hz (the same as my old one), all the stuttering goes away.

Is the monitor faulty? Kind of defeats the object of having a high frame rate if I can't use it...

Tested on two different PCs, with the resolution lowered to 2560x1440.

Have you tested the monitor to see if it happens on other games? If Forza Horizon 5 has a forum you could check there to see if anyone else is having the same problem and hopefully a fix.