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Hyundai Elantra (2001) OBD Code - "Cylinder 3 misfire"

After the check engine light and an OBD scan turned up “cylinder 3 misfire” I changed the spark plug wires and just cylinder 3 spark plug. Reset the light.

The light stayed off a few days, then came back on. Seems to be more prevalent when humid (Colorado is usually quite dry.)

What is my next step?

After a code is erased, it will take several “trips” for a misfire code to cause the check engine light to come on, again. The “trips” may spread over several days.
It can be difficult to find something (a fault) that is there at one time, but, gone another. This is when I like to substitute parts, as opposed ed to installing new parts.
Erase the code. Swap #3 fuel injector with another. Drive the car enough “trips” for a code to set. When it does set the check engine light, read the code to see which cylinder the code shows as misfiring. If the misfire code moved to the cylinder you swapped with (say P0302, for cylinder #2), you then know the fuel injector is at fault.
If the misfire stayed at cylinder #3 (P0303), the #3 ignition circuit is in question. Swap #3 ignition coil with another. Use the same routine that you used with the fuel injector swap.
If the code is still P0303, you’ll have to follow the troubleshooting charts for MISFIRE.

missfires are one trip codes,and have been that way forever,no manf. wants to buy CATS.this car only has one coil pack,so do the injector swap,or just do a running compression check,and vac check,mechanical,.