Ok so I thought it I was having a cold start problem so I changed the spark plugs but it's still doing the same thing....

At a cold start the engine's not doing what its supposed to do. It doesn't fire up to 3k rpms, drop to 1.5k, then even out between 750 and 600 at the end. When I fire it up at cold start the engine kinda sputters below 1k. Then i'll give it a little gas and it'll go to 2k and idle there until I start driving it. The whole time it's warming it's misfiring a little bit, and it did all that before I changed the spark plugs. After it's warmed up it seems to run fine and hot starts fine. Is it a fuel injection problem? Timing?

help a brotha out