My Bonneville is misfiring. It began a couple of weeks ago. It started fine and would drive smooth until the engine warmed up (gauge at ~ 150). Then it would begin to sputter and misfire during accelleration and then even at crusing speeds 45 - 65 mph. Engine light is on.

However, now it begins to sputter from cold start. Really running ragged. Any thoughts on what might be the problem. Thanks!

If you have an engine light, the computer has set a trouble code. Pull the code, or take it to an auto parts store, or mechanic and have it pulled. That should tell you where to look for the problem.