There are several reasons why a Chevy could be idling rough. These reasons include bad spark plugs/wires, fuel injector problems, a crack or break in the ignition wires, simply having a bad grade of gasoline or even a damaged carburetor.
Rough idling can be anything from a slight shaking while sitting at a stop light to feeling as though the vehicle is not getting enough gas to it while driving, resulting in the feel of the car being sluggish. It is hard to pinpoint what could be causing any rough idle since there are so many potential causes. The most common is a bad spark plug or wire. It is recommended that spark plugs be changed every 70,000 to 100,000 miles, depending upon the make and model. Just one bad spark plug can greatly affect the way a vehicle runs.
The second most common reason for rough idling is bad gas or fuel injector issues. Usually, mechanics recommend adding in a gas treatment to clear up the problem. If this fixes the idling issues, then drivers know that their gas or fuel injector was clogged. However, in extreme cases, fuel injectors may have to be replaced if there is a lot of build-up.
Finding out the reason for rough idling is a game of chance. Start with the most obvious cause and work through the different causes until the rough idling issue is resolved.