Fallout 3: Troubleshooting
The game crashes immediately on the first load screen
The most common cause is an installed mod that has another mod as its master that you do not have installed. MO users will be able to troubleshoot this easily as the program auto-detects this problem. NMM users will have to inspect each mod's description for dependencies. Either install the missing master mod or uninstall the problem mod.
The game freezes up and crashes when attempting to choose a perk during level up
This problem has been linked to various mods and the Broken Steel DLC. However, the most likely culprit is game save corruption as a result of too much installing and uninstalling of mods after a game has begun. Unless you can isolate the problem to a specific mod, your only option is to abandon your save and start over. It's always best to start a game that you actually care about with all your mods pre-installed to minimize the effects of game save corruption. Also be sure to use an alternate save mod like CASM.
The game runs slowly, has a low framerate and/or freezes up at times
In most cases you're game is running out of memory to access and this can happen on any PC, regardless of its computing power or system memory. Unless you're running an old PC with low specs, the problem usually comes down to having installed too many hi-res texture packs, script-intensive mods, and/or mods that add a lot of new items or NPCs. Due to its age and requirement to fit the system specs of outdated, 32-bit gaming consoles, by design, FO3 is limited to accessing 2GB of system RAM and it doesn't make use of multicore processors. Adjustments as outlined in my Tweaks section can overcome both of these problems. There is still a limit to the quality of modded textures although having additional video RAM helps. Another cause of low framerates could be the use of an ENB preset which will in most cases result in a loss of 10-30 FPS depending on configuration and system specs. Too many script-related mods that control elements like random events and dynamic weather patterns can also slow the game down. It's usually best to keep these mods to a minimum as they are notorious for introducing irreversible game save bloat and bugs.
Textures are not loading correctly (appearing invisible, pink, mismatched, or as a place holder)
A common texture problem in FO3 is a custom nude skin not loading correctly and instead displaying topless NPC's with no skin detail apart from low-resolution black undies. This and many similar problems are usually attributed to the user forgetting to run Archive Invalidation. MO does it automatically but NMM users will have to toggle the function off and on manually from the dropdown menu each time they make texture-related changes to the game. Other causes could be that mod textures were not installed or ended up in the wrong directory. This is likely to occur if dropping mod assets directly into the Data folder or re-packaging select mod assets into a new archive for installation through a mod management program like MO or NMM. Regardless of how you install a mod it's always a good practice to inspect the folder path of mod assets to make sure it's correct.
Lighting issues such as shadow seams and texture flickering as you move about
If you are seeing problems where walls and floors are not displaying light and shadows correctly as you move through an area this is most likely due to a lighting mod that is introducing elements that the game's flawed/buggy engine cannot process correctly. One of the main culprits is the popular Fallout Street Lights mod. There is no solution apart from disabling the problem mod.
The most common cause is an installed mod that has another mod as its master that you do not have installed. MO users will be able to troubleshoot this easily as the program auto-detects this problem. NMM users will have to inspect each mod's description for dependencies. Either install the missing master mod or uninstall the problem mod.
The game freezes up and crashes when attempting to choose a perk during level up
This problem has been linked to various mods and the Broken Steel DLC. However, the most likely culprit is game save corruption as a result of too much installing and uninstalling of mods after a game has begun. Unless you can isolate the problem to a specific mod, your only option is to abandon your save and start over. It's always best to start a game that you actually care about with all your mods pre-installed to minimize the effects of game save corruption. Also be sure to use an alternate save mod like CASM.
The game runs slowly, has a low framerate and/or freezes up at times
In most cases you're game is running out of memory to access and this can happen on any PC, regardless of its computing power or system memory. Unless you're running an old PC with low specs, the problem usually comes down to having installed too many hi-res texture packs, script-intensive mods, and/or mods that add a lot of new items or NPCs. Due to its age and requirement to fit the system specs of outdated, 32-bit gaming consoles, by design, FO3 is limited to accessing 2GB of system RAM and it doesn't make use of multicore processors. Adjustments as outlined in my Tweaks section can overcome both of these problems. There is still a limit to the quality of modded textures although having additional video RAM helps. Another cause of low framerates could be the use of an ENB preset which will in most cases result in a loss of 10-30 FPS depending on configuration and system specs. Too many script-related mods that control elements like random events and dynamic weather patterns can also slow the game down. It's usually best to keep these mods to a minimum as they are notorious for introducing irreversible game save bloat and bugs.
Textures are not loading correctly (appearing invisible, pink, mismatched, or as a place holder)
A common texture problem in FO3 is a custom nude skin not loading correctly and instead displaying topless NPC's with no skin detail apart from low-resolution black undies. This and many similar problems are usually attributed to the user forgetting to run Archive Invalidation. MO does it automatically but NMM users will have to toggle the function off and on manually from the dropdown menu each time they make texture-related changes to the game. Other causes could be that mod textures were not installed or ended up in the wrong directory. This is likely to occur if dropping mod assets directly into the Data folder or re-packaging select mod assets into a new archive for installation through a mod management program like MO or NMM. Regardless of how you install a mod it's always a good practice to inspect the folder path of mod assets to make sure it's correct.
Lighting issues such as shadow seams and texture flickering as you move about
If you are seeing problems where walls and floors are not displaying light and shadows correctly as you move through an area this is most likely due to a lighting mod that is introducing elements that the game's flawed/buggy engine cannot process correctly. One of the main culprits is the popular Fallout Street Lights mod. There is no solution apart from disabling the problem mod.