P0301, P0302, P0304, P0300 are all misfire codes meaning something is disrupting the air/fuel mixture in cylinder: 1, 2 and 4. P0300 is a random misfire
P0420 is the vehicle's computer has detected the catalytic converter is no longer reducing emissions out the tailpipe (it could also be related to the oxygen sensor cause this code). This could be due to the misfire damaging the catalyst.
I want you to do some basic checks. Check the engine oil level, transmission oil level (after driving awhile then checking fluid level with the engine off), and unbolt the one bolt on each ignition coil. Start the engine look at each ignition coil (use a flashlight) do any of them get push up or move? If not, good. If it does move and you can smell a fuel smell or an exhaust odor then suspect that spark plug for looseness.
If you hear a ticking noise when first starting (gets louder with engine speed) the engine when cold you might have a exhaust leak causing the odor.
What spark plugs did you use (brand and style like platinum, iridium, etc.)
There are a few components that can cause a misfire. Typically, on Hondas a misfire is cause by the spark plugs, spark plugs being loose, Ignition coils, and valve lash clearance (there is more components). If the spark plugs are of good quality then it is probably safe to say the plugs are not causing the misfire. If the shop replaced cylinder 2 coil its probably not that coil causing a misfire.
Answer my question and do those checks I mentioned and get back to me. I threw a lot at you. So, let me know and we will go from here.
Friday, March 1st, 2019 AT 8:14 PM