How to fix P0300 and P0302 error codes for Hyundai Accent 2008?

Question

Make: Hyundai

Model: Accent

Engine: 1.6L

Year: 2008

Error codes: P0300,P0302

Knowledge level: I know little about cars

Help needed: Please help me find out what is going on and how to fix it.

Answer 1

P0300 is the trouble code for random/multiple misfires. P0302 is the trouble code for misfires in cylinder #2.

Common causes for misfires are :

• Bad spark plugs. Remove them and inspect them. Replace them if necessary ($20 if you do it yourself). Tools needed: ratchet with various size sockets, spark plug socket, ratchet extension, spark plug gapper tool. First remove the plastic cover, then you will have the 4 ignition coils accessible. Twist them and yank them, they are really on there. Look deep inside the engine hole, that's the top of your spark plug. Use a spark plug socket and a ratchet extension and unscrew it, when it's loose, pull it out and compare it to this chart and measure the gap between the curvy part and the thin grain of rice part. I believe the gap needed for your case is 0.045". If the gap is too big, gently tap the curvy part against something hard. If it's too small, use the gapper tool to gently pry it open. We are talking fractions of an inch, so just apply some mild force, less than opening a can of pop, and measure. New spark plugs need to have their gap checked the same way.
• Bad ignition coils If changing the spark plugs doesn't prevent your problem from reappearing, your next likely culprit are the ignition coils. They are about $20 each, replace the entire set. Only remove them 1 at a time, because the order they are connected in matters. Remove one, replace it. Then move to the next one.
• Bad injector There isn't an easy way to diagnose a bad injector and replacing them involved releaving fuel pressure, that may be too dangerous for a novice.