My 09 Chevy cobalt has check engine light on I changed sparks plugs. Coil plugs and still idles like it wants to shut off?

You need to get the vehicle scanned for trouble codes to know what to fix. An auto parts store will do this for you. Write down the codes.

I have a 05 cobalt, when I first bought it a couple of months ago, it had the same problem. The problem was easy to fix. It had about 120,000 miles on it and the fuel injectors had some sludge built up in them. I filled the gas tank premium (expensive) gas, which may or may not have helped, and poured about half a can of seafoam brand fuel injector cleaner into the gas tank. The car spit out some black smoke from the exhaust pipe for a little while (burning off the carbon build up in the engine and fuel system). And thats it, problem fixed. I would still have the auto parts place check the engine codes while your there. But hopefully it's just an easy fix.