I have a 1973 Mach 1.. I've noticed that the car will die when stopped. I changed the in-line fuel filter that didn't help. I've never had the car act this way before.. I've had the car tuned up in the past so I'm not sure what's going. Is there another fuel filter on the car? Fuel pump going out? Any suggestions??
Your problem doesn't sound like a fuel filter issue. If it was a fuel filter issue the problem would also show itself at other RPM's.
It sounds like you have an idle mixture problem or vacuum problem.
Accelerator pump? Id start with the carb.
Could be the carb needle and seat, this can send the whole system into havoc, take out a couple of plugs and see how they look, its a cheap and easy fix if thats the cause.
I would start off with the obvious, checking spark plugs, looking for a vacuum leak. Is you idle too low. Did you do anything to the car before you it started stalling when stopped? Could be carburetor related, possibly a float adjustment. Check your engine's diagnostics to determine if they are within specs.