i may be having the same issue with my 95 caravan. Without warning, the gas pedal will only move about 1/2 an inch. If i stomp on it extremely hard, it pops into neutral. It moves perfectly normal in park, and neutral seemed good as well. I sprayed the linkage, which didn't affect anything.
I did notice when in gear where the linkage connects to the throttle, a flat plate about 3" or 4", with a sliding slot that allows the gas pedal to move. When in gear, this plate lowers, which reduces the slot space. Nothing looks bent or anything like that. Any ideas? Could it be a sensor some where? Transmission?