My car has had pretty rough idling over the last several weeks regardless of whether it’s in neutral, drive, or parked. I figured it was a spark plug and/or ignition coil issue, and thanks to my check engine light finally coming on, I was able to identify the problem as a misfire in cylinder #3 via free diagnostics run by Advanced Auto Parts. I picked up a compatible ignition coil (~$40) and iridium spark plug (~$10) and went to work!
After removing the ignition coil corresponding to cylinder #3, I examined the spark plug (all of which I replaced several years ago) and found no obvious problems with corrosion. I decided to just change the ignition coil. This component is responsible for delivering high voltage current to drive the spark plug and ignite the air/fuel mixture in the piston cylinder.
Took me about 20 minutes, saved $150 dollars, fixed the idling problem, and realized that I really… REALLY needed to wash my engine. 😀