Engine condition is stored in state.cfg, which is in your AppData folder for MSFS. The location differs based on your platform, so it's best to google it for the most accurate location. You should be able to make this change to get the effect you're looking for, but I still feel bad about your original problem, even if I'm not supporting the aircraft in MSFS 2024. It seems that many user are still able to use the aircraft in MSFS 2024 with no problems, so I do have to suspect that this is something local. The best guess I can offer is that the grey screens are the result of an avionics server crash. In order for this to only affect you, then it must be some 3rd party application or avionics running on your side. I know that's a bit of a broken record, but it's the best I have to offer.
If you wanted to do some deeper exploring, the CoherentGT Debugger might offer some error messages that could be helpful in determining what's going on. I'm not sure if this will work without the SDK installed with developer mode running, but you can try entering http://127.0.0.1:19999/ into the URL bar in your web browser. If you get a bunch of blue links, please let me know, and I can tell you where to go from there.