1999 Dodge Ram Engine Noises

One day when I went to start my truck it failed to start. It would crank but the engine would not start. Eventually after repeatedly opening the throttle while trying to start the engine the engine fired up. When it started, it had been sitting in cold weather for about ten days. The engine was running slightly rough and coming from under the engine was a loud popping noise that occurs when the truck is sitting still. When the noise occurs, the exhaust output is increased in puffs of air coming from the exhaust pipe. I was wondering if you had any idea what could be causing this and what my next step should be.