Chrysler Repair: Bad egr?, fuel air mixture, changing spark plugs

Question
QUESTION: Hi Roland,

I have a 2006 Chrysler 300CAWD 5.7 Hemi. My car wouldn't start one day and since then I've been having problems. No symptoms up to the day it wouldn't start. I finally got it started, but loud knocking and very hard idling. I haven't drove it far distances because it dies at low speeds or when I stop. It doesn't die if I leave it in park but idels very rough. Check engine light came on and codes were P0300 and P0306. I changed all spark plugs yesterday but still having same problem. My next step was to change the coil packs but 8 coil packs at $30 and not knowing that's the problem for sure kinda bothers me. Could it be my egr? It's $40 and seems easy to replace but don't want to bother if its not that either. Any advice would be great

ANSWER: Hi Jamie,
I would say with no codes that the egr might be suspect for hard starting and poor idling. But with the specific codes I believe that a focus on the 'miss' on cyl 6 would be a better approach. It might be a fuel injector not working on that cylinder or a mechanical problem which you could check first by removing the spark plug an checking the compression. By loud knocking do you mean it sounds to be mechanical interferenced of some sort? An egr valve sticking slightly ajar will cause a fuel/air mixture problem, but not typically knocking per se. But let me check the shop manual and get back with any further suggestions for the 306 code, later today.
Roland
PS Please 'rate' my answer (aee below).
Thanks,
Roland

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QUESTION: I'm sorry I should have specified the knocking has since stopped. It was just that first day when I couldn't get it started, it knocked after I got it started. Also after changing spark plugs do I have to clear the engine light and see if it comes back with same codes, or does that reset itself? Thanks again

ANSWER: Disconnecting the battery for a minute will usually clear the codes. Then drive it again and see if they return. I revised my first answer, also.

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QUESTION: Haysjam26atyahoo.com. Thanks so much!!

Answer
Hi Jamie,
Would you try the code erase, drive it again until the  check engine light comes on again, and verify that the code is still 0306? Then let me know. Because it takes me probably a half hour to copy and send 10 pages I would like to be sure that the code is still there. Thanks,
Roland