Ok let's see if we can get your GTAIV running at optimal performance.

Firstly go to "properties" on your Gta IV by right clicking on it in your steam library. Set your resolution with a dash. (Example: -width 1366 -height 768).

Then, set another command with a dash and put the following: -availablevidmem 8. What this does is place more mb to your vram to make you change settings.

Lastly, add the last command which is "-norestrictions" and this will allow you to freely change your graphics settings.

Once you have done these steps launch GTAIV and begin tweaking your graphics settings. Since you have now used the advanced launch settings I have provided, the settings will actually take effect now due to the default console "restrictions" set by the developers and never changed for the pc release.

Get back to me once this is accomplished and we'll go from there.

Later bro