I have a very odd problem and hard to describe, so I will put it in a list:

1) Only when car sits over night.
2) Only when it has been raining all night or is really damp.
3) When start the car, it will idle roughly and want to stall out.
4) When I drive the car, it will want to die out when I first press on the gas, but once it gets going it stops wanting to die out.
5) This problem will continue until I drive the car for about 15 minutes, then the problem will be gone for the rest of the day.

It's almost like some engine part is developing moisture from sitting but dries off from driving after 15 minutes. But that is just my guess.

Any suggestions on what it could be?

I just had a tune up 2 years ago with a new wires and rotary cap if that matters.

 

Some damp dreary morning when you feel it would act up, pull the distributor cap and look in it for condensation. Also look for hairline cracks that might let moisture in. Of course, it's equally possible there is an electrical connection hidden away somewhere that allows moisture in. The cap is a good place to start though. Another thing I have done that occasionally works is to fire it up when dark, pop the hood and see if any of the ignition wires are "leaking". I've seen spark run out of the boot and onto the block before...

 

i have a leak in my firewall somewhere, because when it rains the passenger flood board carpet get's wet. i think it may be the seal in the front windshield, not sure though. is there an electrical component in that area that could be getting wet?

 

Yes indeed. Both the Ignition Control Unit and the Engine Control Unit are in the vicinity along w/ a huge bundle of wiring that passes through the firewall. In the following pic, you're looking in from the driver door at the front of the cabin. Both firewall panels have been removed so you see a bit of the engine compartment beyond. To the right of the passenger side firewall opening, you will see the ECU mounted on the kick panel area. The ICU actually mounts to the firewall panel which is missing in the pic. It may very well be the wind screen that is leaking, but I'd give equal suspicion to the louvers/vents in front of the windshield. Water that enters here is supposed to leak out under the edge of the car where the sides meet the bottom of the car. Every so often (12" or so) you will see wider weep holes where water runs out. These get clogged over time with dirt and debris. An air hose, small screwdriver and imagination are needed to get them cleared out. A water hose run through the louvers will tell you quickly if they are draining properly.