Engine light came on and plugged my OBD ll with code; P0302 which is cylinder 2 misfire. So I replaced the coil plus changed all 4 spark plugs. After 2 days the light came back on. Is cylinder 2 the 2nd from left? (which I changed) So does anyone know what else may cause the misfire?

 

Cylinder numbering starts at the front of the engine, which is on the passenger side of the car. The left is considered the driver's side. If you have changed the proper coil, other possible causes are fuel injector or internal mechanical issues(low compression). If you don't have a compression tester, most auto parts stores will "loan" one to you. Usually you buy it, and have 90 days to return it for a full refund.

 

You changed the plug, now swap #2 coil for #4 cool coil and see if the code comes back to P0304. Then it could be the coil.
Also double check the wires and connections to the coil

 

At least you got a check engine code. I had an issue a couple of years ago where our HHR would keep jerking loosing power whenever I had to give it gas going up a large hill with no engine code being displayed. Suspecting that it could be a weak coil, I went ahead and replaced all 4 coils and viola, the problem disappeared. It was cheaper to buy and replace all 4 coils from Rock Auto than it would have costed for a diagnostic at the stealer. I also figured that if one was causing problems the other ones probably wouldn't be that far behind.

As the others have pointed out, your misfire can only be the coil, plug, injector, or low compression.