2010 hhr lt trouble code po302 and p0300
 

Ok, REALLY NEED HELP , I HAVE A 2010 HHR LT WITH TROUBLE CODES PO302 AND P0300. I HAVE PUT NEW SPARK PLUGS IN , A NEW COIL, AND COIL WIRE CONNECTOR , EVERY THING THE DEALER SAID NEED TO BE DONE FIRST TO RULE OUT ANY OF THOSE POSSIBLE ISSUES. I STILL HAVE THE SAME CODES POP UP AFTER A FEW DRIVES AND IT SEEMS TO COME BACK WHEN THE CAR IS AT IDLE, PLEASE ANY HELP WOULD BE GREAT , I AM RUNNING OUT OF IDEAS.

Welcome to the site, first lets take off the caps lock, have a look at this video, Please watch it all, and maybe the part about the battery will be the key to this problem.
Also the ground connection at the front of the transmission to the rad cradle up by the front of the engine bay on the drivers side.




I sure hope this helps, now on a 2010 that's roughly 4 1/2 to 5 years old for the original battery, please have it checked out at your local AZ or O'R auto parts store.
I do mean fully checked out, load test and all, these HHR's tend to react funny when not dealing with a full charge

Thank you Oldblue , i have done all that
 

Oldblue , i have a new battery , new spark plugs , coil in cylinder 2 , checked all hoses and all seem fine, i can say that i did have a problem with the ground on the battery where it has a problem starting so i checked the battery and the ground was lose , but i fixed it and again it is a new battery and the problem is still happening . The only thing i have not tried that you suggested was the ( the ground connection at the front of the transmission to the rad cradle up by the front of the engine bay on the drivers side.) i dont know where to check for that , do you have a picture or diagram i can look at , i am willing to try anything at this point, thank you again for all your help

I suggest compression and leakdown testing. If that is clean look at injectors.

The p0300 will go away once the #2 cylinder stops misfiring (p0302).

Ok , now you didn't say about the new battery in your first post, that's OK , now this needs to be done after you have gone into the spare tire area and disconnected the ground wire to avoid any sparks, shorts or computers toasted. place a towel over the rear hatch latch so if you do close the lift gate it won't lock you out.
Oh, you would be surprised. how often I've seen that done

now, open up the hood and look for a 10mm nut up front on the rad cradle on the drivers side, make sure it is clean and tight, now follow it down to the front of the transmission just below and to the drivers side of the oil filter cap. this should also be clean and tight.
under the hood again look for the fuse box , take the cover off, ensure the two halves are tight they are 10mm bolts, the positive connection on the left side of the box is a 13 mm nut, make sure it is clean and tight.
I don't have a picture here on my PC and it's 8 degrees out there today up here, so I do apologize for that, I'm sure you will find these points.

Now tighten the positive cable first back at the battery and then the negative cable , again to avoid a short , spark or have no-panS burned into the palm of your hand.

thread moved to the more appropriate Problems/Service/Repairs forum.

hahahha , i got you
 

I see , and i will check those cables , thanks for the detail description on the location of them. I also saw on another forum that because the symptoms sound the same as " it seems to get those code after driving a while or at idle for a while" and after doing all that i did , said to do a compression and leakdown testing. So after i check the wires and if they are all good then i will take it to the dealer and have them do the testing since i still have warranty on powertrain since i only have 96000 miles on it, so if there is an issue, it should be covered . Thank you very much for all your help

Welcome! If it is under warranty , and just for fun swap out #2 plug and coil for #4 plug and coil pack and see if the code changes to P0304, you can get the codes checked mostly for free at AutoZone or O'reilly's like parts stores.

Saw on another forum? Maybe it was in Post #4 in this thread?

It very well could be , but let's check things out and ensure the problem gets fixed.
I'd suggest compression test and leak down test after the simple things are checked, redundant as they may seem.