A flashing Check Engine light means stop the engine immediately to prevent damage to the catalytic converter. Too much raw fuel is going into it and will cause it to overheat.
The rough running is the proof there is a misfire. That means there is unburned fuel, (and air) leaving the engine. It could be as simple as an overdue tune-up. New spark plugs and wires might solve the problem. GM also has a huge problem with their injectors. They are the only company that doesn't flow match them on the assembly line. They just stuff in a handful out of the bin. When they don't flow at the same rates, one cylinder will always be too lean, and the oxygen sensor will pick that up and tell the Engine Computer to add fuel to ALL of the cylinders on that side of the engine. Very often that doesn't show up until the the engine has high mileage and other things need attention, such as that tune-up.
Most mechanics start with the tune-up and hope that is all that's needed, but don't be surprised if the Check Engine light continues to turn on after that and more diagnosis is required.
Tuesday, April 5th, 2011 AT 8:03 PM