Hi. My check engine light recently came on. Went to the auto parts to have it checked out and it threw a P0300(cylinder misfire-random) & P0456(evap small leak) code. Has anyone run into this problem. If so what do you all suggest me to do. Any help is apreciated. Thanks

 

The P0300 misfire code could run something simple as a fouled plug, or a coil-pack starting to break down? It's easier when you can tell Which cylinder is mis-firing.

The evap could be your purge solenoid on the gas tank... or just your gas cap being loose...

Trouble shooting online is a pain in the butt really, but eventually, you'll get the suggestion that fixes the issue...

Good luck!

 

Most of the time if it was the gas cap the DIC would display CHECK GAS CAP

 

Yeah. My DIC would sometimes didplay Check Gas Cap but it hasnt been showing lately. On the misfire its random. No specific cylinder.

 

And I assume you have an LSJ if you posted this question in the correct category, but just to make sure, what year/trim is your cobalt?

 

I had p0300 on startup for awhile, swapped in plugs gapped at .032 and the problem went away but my car is an LNF. start with plug gaps then go from there

 

I have a 06 Chevrolet Cobalt SS Supercharged with stage 2 pulley and injectors and other mods. I heard from other member about switching to NGK's Copper Cold spark plugs. I dont know if that could make a change. Also about spraying carb cleaner around the intake to see if I have a leak on the gasket. My spark plugs are supposed to be gapped at .040 but since I got the iridiums I didnt wanted to mess with them. Ima check em out today and try to re-gap em. Im going to disconnect the battery to clear out codes and see if my CEL light doesnt come on again.