I own a 2009 Cobalt sedan. If I let the car idle for longer than a minute or two the engine will set a P0308 DTC (Injector #1 misfire) and the transmission will shift extremely hard. In this situation, I usually will shut the car off, let it set for 30 seconds and restart and drive before I let it idle very long. Also, I've noticed a severe engine miss will occur if I'm stopped at a traffic light for very long - as soon as I pull away, the issue usually will go away. I've inspected the harness, replaced all four spark plugs and installed a new coil at #1 cylinder. The issue remains - however it is intermittent. I can go two weeks without a DTC being set, then I'll have 5-6 days where it's constantly an issue. I've had the ignition recall done (I was promised a gift certificate from GM - which they never sent me....) I spoke with the service manager and he wanted to charge me $120 to pull the code and diagnose for one hour. I respectfully declined his offer - $120 is a lot of money for Cobalt owners.... Any suggestions?

 

Try this remove the bolt from the #1 cylinder coil start the engine and slowly pull coil from the spark plug until you hear the spark jump if you dont hear the spark jump the the coil is not firing and could be a wiring problem or if you do hear a jump maybe a fuel injector problem, if no spark move coil to another cylinder and start the engine again pull coil from spark plug if it starts jumping spark you know coil is good.