I have an 05 Trailblazer with an in-line 6. After driving to Oklahoma from Michigan recently my truck started to act like it had a miss in the ignition while idling. When I would get the vehicle on the road it seemed like it would buck once in a while like I had the miss and the cruise control would not kick in. At the same time the engine light would flash. I have just returned home to Michigan and would experience the same symptoms. Could this be just a spark plug issue or should I be concerned about a more expensive problem?