IF THE SAVEGAME IS PRIORITY TO YOUR GAMEPLAY:
It is more than likely that you are using a corrupt savegame. If it works fine to everybody else, you can use a mod software that is called OpenIV. I use this software to mod as well.
What I do to install my GTA IV Savegames:
1. Reinstall lcpdfr and select xliveless for an asi loader if you do not plan to play on multiplayer. Our main issue is the GFWL client, so it is best to get that out of the way.
2. Delete your savegame and proceed to download and install OpenIV (Same as Spark Iv with a much more user friendly interface.)
3. Run OpenIV and click on your game, give the steam path (C:Program Files (x86)SteamsteamappscommonGrand Theft Auto IV) and you will be greeted with a screen that shows game files (Models, data, etc.)
4. Navigate to user data and you will see a savegame. If you do not see a savegame, don't panic. Enter edit mode and drop your savegame into the user data folder whether you see a savegame or not.
IMPORTANT!!!:
If you see a savegame inside the user data folder, extract your savegame to the desktop and replace the current savegame with the new one.
Report back with any questions. :)