But what does that mean

Do you mean misfire on cylinder 2? If so, you may need to change the spark plugs with the same ACDelco platinum plugs that are in the engine. Be sure to have them gapped to spec. If the problem persists, consider replacing the coil going to cylinder 2. Lightly coat the porcelein portion of the plugs, and the top electrode, with dielectric grease--this helps prevent misfires.