I was driving home a few days ago in some rain, and when I came to a stop, I noticed that my Tahoe was idling a little rough. When I let off the brake to just idle up in traffic, the truck was jumping. Like it wasn't firing right or something? Either way, it did it the entire time it was raining. Never really noticed any difference while I was actually driving, just when I was idling in traffic. Truck was moving, but no throttle. Just idling in Drive. Any ideas on what this could be? Bad wires? Coil?