I have this buick for about a year, and I have replaced the coil packs, spark plugs, wires, housing, ignition modual, and crankshaft or camshaft positioning sensor, and it still runs as if it is running on only 2 cylinders. No power on driving, runs rough on startup and still missfires. Spent over $400.00 on this and nothing seems to work. This problem has happened last year about this time, and I only replaced the plugs and housing at that time. Its just this time, it is becomming a pain in the butt. I have exauhsted my nerves on this and need some help. The check engine light does not come on, and it is not a light bulb, but a LED. The service light used to come on, but not anymore. Could the LED have gone out and caused all of these problems? Apparently, I am in the wrong forum to ask this question, thanks for looking, and the help.