Why does my car idle rough when I'm parked or picking up speed or driving slowly?

I'm confused. Basically, your car can idle in only two ways, either in park or in gear with your foot on the brake and the vehicle motionless. The way the car behaves in those conditions is very telling to a trained mechanic. Some people will say the car is still idling if you take your foot off the brake but don't give it gas. (If the idle is set to high, the car might move pretty quick. That is undesirable.) That might be a third idle situation. Your car is not idling if it's accelerating. And if you are coasting and slowing down from cruising speed, the engine rpm will be higher than idle speed. So, that's not idling, either. It sounds like your car is always running rough.