Every once in a while when I start my engine it wont be running on all 8 cylinders, but after a few minutes the last one kicks in. For example, I started it up and it ran great, drove to the store, when I got back in the truck and started the engine, It was only running on 7. I just replaced the plugs, wires, distributor cap and rotor a few weeks ago the first time this happened. Is it just because of the cold weather here in Montana? cause once it's warm it runs fine, anything I can do to fix it?