In this video I'll demonstrate how I diagnosed and fixed cylinder misfire codes P0300, P0301 and P0302 performed on a 2013 Hyundai Elantra 1.8L I4. P0300 is random cylinder misfire (meaning more than one cylinder) and P0301 and P0302 being cylinders 1 and 2 respectively. I started by assuming its an ignition problem; either spark plugs and/or coil packs. If a spark plug or coil pack replacement doesn't fix the problem, then I figured it's a inadequate fuel delivery problem (i.e. the fuel injectors). A clogged fuel filter or a weak or faulty fuel pump would make all the cylinders misfire.
After replacing the spark plugs, the misfire stopped on cylinder 2 but continued on cylinder 1. I then swapped the coil pack in cylinder 1 with cylinder 4. The misfire continued on cylinder 1 so I figured it was potentially a fuel injector problem. I then swapped cylinder 1's fuel injector with cylinder 4. Low and behold; cylinder 4 misfired while cylinder 1 ran normally. Cylinder 4's injector was replaced with a new one and the problem disappeared. Engine now runs fine.

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Parts & Specialty Tools:

Push Pin Pliers (For disconnecting fuel injector electrical plugs)
https://amzn.to/3Ut6b1G

Permatex 22058 Dielectric Tune-Up Grease, 3oz. (Used to coat the fuel injectors o rings)
https://amzn.to/3YrgFAX

Cotton Swabs (for transferring the dielectric grease into the fuel injector rail ports)
https://amzn.to/4dXULKo

SE 30-inch Telescoping Magnetic Pick-Up Tool (Use a 16mm deep socket to loosen the plugs and this magnetic pick-up to get the them out)
https://amzn.to/4fdSAmN

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