Misfire Hell!
 

Last night, I threw my 2007 Accent into reverse to back out of a driveway when I noticed a weird shaking. When I began driving, I noticed the engine light was flashing. I took it to AutoZone and they read a P0303 code which is a misfire in cylinder #3. Instead of wasting a million dollars on a diagnosis from a mechanic, I decided to replace all the spark plugs since they cold be the culprit, and it couldn't really hurt for the little money it costs to buy them. I successfully changed them out today, and much to my surprise... little to no difference. I unplugged the battery and started it up again, took a little drive around town, and my baby was driving a little funny! The engine light came on almost immediately and it felt like I was driving 3/4 of my Accent.

Anyways, I got tricky and decided it could be one of the coils, so I switched the #2 and #3 coils with each other to see if I would get #2 misfiring. Wish granted... except now #1 is misfiring too?

WHATS GOING ON!?

SOLUTION!

I had to break down and go to a mechanic. They diagnosed it... bad ignition coil. Good thing I ruled that out with my little test...

Basically when I moved the bad ignition coil from 3 into 2, it cause 1 and 2 to malfunction since they feed into the same area from what I understand.

Oh well. It's about an $80 part with a little extra for labor. It's probably best I let them take care of it since they guarantee their work.

This troubleshoot session failed for me, but maybe I can save someone else some money.