cylinder that's not firing

Hi All.

I searched on this but didn’t find answers to my question…

My car has a bouncy idle… 1K to 2.5 K
I noticed a while ago, before I stored the car for the winter, that she only ran on 3 Cyl !!! I know what you’re thinking : “why didn’t he notice this before?” well, I don’t know.

Anyway, could this non-firing cylinder be the source of my bouncy idle?

tx.

i dont think da bouncy idle is from da 3cylinders cuz i have all four cylinders runnin but i also have dat bouncy idle it does it sometimes and when it does it bounces from 2rpm and goes as low as like .500rpm and once in a bue moon when its bouncy da check engine light comes on so im tryin to figure whats up also im thinkin it just needs a good maintenance tune-up bt if anybody knows whas da exact problem id appreciate it much