Idle problem and down shifting problem.

Ok I have a 92 Chevy Lumina Euro edition and it runs great but these two problems I found very irratating. When I run my car on idle with my foot on the break for a few minutes it will die. I told my brother this he said all luminas do that. That didnt help me a bit I want this problem fixed thats why I asked lol. I just feel like a idiot when its stalls on the street or when im driving out of the lot. It will only stall on rainy days or the day after it rained if I leave it idleing for awhile. My solution was that I would put my left foot on my break and have my right foot on the gas a bit so it can idle higher. I think it has a bad slow idle or something im not that much mechanically inclined but I know some stuff.

Ok thats the first problem now on to the second. When I am on the interstate or on a fast lane so to speek I will speed up. But if there is a slow car coming up I will have to let go of the gas. When I do this my car jumps or shakes or something I feel a big jerk in the back. So when I down shift my back end jerks or something whatever its called. It just feels like something pushed the back end of my car when I do this. So long story short. When I speed up and llet my foot of the gas it will do this. Oh its a automatic to just to let you guys know. If anyone has any suggestions please let me know.

Your coilpacks and ignition module are up near the front of the motor, where they can get wet. They were moved to the rear on later models. You might want to try spraying them with some WD-40 before the next rain and see if that helps. Your plug wires might also be shot. That's a common cause of that behavior when related to humid conditions. If you bend one into a tight loop and look closely, you may see small cracks in the surface of the wire. If so, that is probably the problem.

The other sounds like it might be a sticking torque convertor lockup that is delaying release when you decellerate, but need more info....