SES light after sitting for 3 months

[Champ]

I'm certain this is been discussed many times in here but I can't find this specific situation. I live in Western NY and garage my 3.0 six speed E85 in November. We've had a mild winter so far, so yesterday I pulled it out for a wee bit of joy riding. My joy was quickly extinguished, however, as it started OK but was idling rough, like there is a misfire. After warming up, I rode off, hoping it would improve, when the Service Engine Soon light came on. Furthermore, it continued to run poorly and bogged down upon acceleration. My question is, what would lead to this problem after sitting idle for 3 months? It ran perfectly prior to garaging. Before I get bent over too bad I'd like to see if there is something I can try.

Thanks in advance.

[j3nks79]

Could be anything. Plug it in and read the codes

[Champ]

UPDATE -
The code is P305, cylinder 5 misfire. Could this mean I need a new coil for cylinder 5, or might it be something more significant. Does anyone have any history with this issue?

[raymond.harper]

Swap the coil pack on number 5 to say number 1. Clear codes then see if a new code appears for cylinder 1. If so, then faulty coil pack