89 Grand marquis
#3
It could be quite a few things the way you are describing it.
If it stalls right away, w/o anything happening in between, that certainly sounds like a fuel issue, that the engine is not getting any fuel.
By stepping on the gas pedal, you're opening up the throttle, the fuel and air mixture is enlarged, but ups: Lots of air, no fuel.
A diagnosis online is hard to do. 89, so carburetor, right? Yes, I would say fuel issue.
Greetings!