Prostart/Autostart 3300CT Problems

The obvious conclusion to draw is that your range increases the higher the remote is relative to to the car. (Nobel prize for me! ) You might notice at ground level if you seem to be out of range, if you hold the remote over your head (maximum reach) and try it again it might work at a slightly longer range. I think the only way you can overcome this is to change the antenna location experimentally. I had a 1994 Cavalier with CommandStart installed back in 1997 and found a similar behaviour (although not as extreme as you report). The antenna on it was installed at the top of the windshield right behind the rearview mirror.