Got a weird problem with 1991 Prelude. The drivers side carpet, and only the drivers side carpet gets wet during a rainstorm. 1) The floormat is dry 2) The headliner is dry, not coming past sunroof 3) The seats and door panel.remains dry, not coming past door seal or window 4) Trunk is dry 5) Car gets wet when at rest, no holes in the floorboard. I've noted there are two drainholes for the sunroof in the forward corners of the roof. What path is the drain line, and is it possible for that drain to back up into the interior?
There is usually a water drain in the fresh air intake to drain away rain water. Perhaps this drain is clogged?
Your best bet is to join www.preludepower.com Just copy & paste your post and start a new topic there and the responses will come flying back.
I had the same problem with a different make of car. Like the other poster said, I think you either have something plugging the HVAC ducts, or the seals have a leak. For me, the rubber seal that joined 2 plastic ducts was defective, causing leaks during an extended rainstorm. I had no leaks when washing the car.