Extreme framerate lag only on WCA and Italy

I have a problem with both West Coast and Italy where when playing under certain circumstances, I only get 3-6 FPS, but on every other map I get 30-60 FPS.
On West Coast, the lag is only triggered by a few things, that being switching windows and back to BeamNG (only sometimes), switching vehicles (only sometimes), or driving into the downtown area. It can temporarily be remedied by turning PostFX off and back on, but the first two triggers can cause it to happen again. If I avoid any of these triggers, I get normal FPS.
On Italy the game lags no matter what, no matter where I am, no matter what I do. I tried the PostFX thing but it didn't stop it.
When this happens, it stresses my GPU and causes other programs to violently stutter, that stuttering does not happen when BeamNG is running normally. I've tried clearing my cache, running in safe mode, reinstalling the game, lowering settings, updating graphics drivers, and rebooting my computer. None of them has worked.

My specs are:
AMD FX-8320, 8 cores @ 3.5 GHz
8 GB DDR3 RAM @ 1600 MHz
NVIDIA GeForce GTX 960, 2 GB
1 TB HDD @ 7200 RPM

 

….Hmmmm....well, Italy is the biggest map yet, and WCUSA still has some performance issues...could be that, but I'm no rocket scientist.

Even if, I don't know much about specs. Maybe someone else could answer better then me?

 

Your CPU is bit weak for those heavy maps, but also you have only 2GB of vram which can be an issue, especially with Italy if you keep graphics details at high.

Your system is capable to run only low to normal settings shadows at partial, not SSAO, no dynamic reflactions. That is in WCUSA and Italy.

Now, 3-6FPS might be related to low vram, or running out of system memory, which would then cause swapping.

As you have only 2GB of vram and 8GB or system ram, Italy will be very tough to get to run properly unless having lower graphics details and thus lower memory usage.

When 2GB of Vram runs out it wants to use system memory, but Italy uses already pretty lot of system memory, I think it was very close to 8GB.

Having browsers, discord etc. running on background will make matter worse. Minimizing OS and other software footprint on system ram will help in such cases.

I think my system uses around 1.7GB of system ram before starting BeamNG, haven't paid much attention to that.

Setting graphics to normal and unchecking SSAO as well as Dynamic reflections, set shadows to partial and test italy again without any other program running and see if that helps to fix the issue.

 

Just how much does closing apps help frame rates on, let’s say WCUSA with 3 vehicles.

 

That depends on programs you close (words I dislike horribly, app and device, these are computers, not phones).

Also depends on CPU, with weak CPU that is hitting very much of it's limits it can be even 10fps with single car.

If your CPU is well able to handle the job, difference is much smaller.

Percentage of single core load that program causes defines FPS gain in such weak CPU at single core limited situation.

In case bad AV it can be even more, when defender had those high CPU usage versions (not sure if they still have) on some situations it was easily 5fps even on my CPU which is quite fast.

There is no way to give general rule as withing single map this changes so much, from one extreme to another really.

 

Out of VRAM.
WC USA & Italy are heavier than other maps. Use medium or LOW with that GPU depending on the map or GPU.
Roane County can use 4GB VRAM on MAX settings without issue. In fact with 1 '88 Pessima in play on game version 0.11 or 0.12 or so, it loaded up around 3843MB~3911MB when 1st loaded. Roane County has a large variation of buildings like WC USA so it's very possible that's the case with WC USA. Video RAM is exponentially faster and much less wait time than system RAM.
When you can afford it, look to purchasing a used 4gb or 8gb model of RX 470, 480, 570, 580 when you can afford it. Plenty of used cards out there. They will have roughly enough power to run most all games at medium to high details at 1080p. I have an RX 480 I got a little over two years ago for about 268$ new at a retail store nearby, it still does quite well. With the recent improvements to the game engine it runs very well, easily keeping over 60fps, and even only down to 45~55fps in one spot (that's all I found) in Italy, all other maps run tops. An RX 580 is about 10~20% more powerful than a RX 480, depending on the brand and core speeds. You can find plenty of them on the used market, sometimes fairly low especially for RX 470 4gb models. So keep eyes peeled.

Shadows are CPU-driven. Keep those to player-only or OFF. Do not use full shadows on AMD FX processors or older non-Zen core APU processors. SSAO also has a significant impact on FPS. Reflections will murder a 960 or lower card, especially on a heavier map, and add A LOT of draw calls (which lags the CPU, further worsening things). So keep reflections off too.

EDIT: Card overheating will also cause a speed drop like this but not QUITE as drastic. I highly doubt it's that.