reduced propulsion power

Hello everyone, I've had my 2011 Volt into the dealership 3 times now with the same problem, and they cannot figure it out. Basically I get the "no codes, so everything is or must be working perfectly". Well, I'm hoping one of you have had this problem (and had someone who knew how to solve...

My 2011 Volt with 89,500 miles ran very rough on the ICE; the engine ignition coil assembly was corroded and needed to be replaced. This was an intermittent problem over about 4 weeks, but the last time it occurred the engine (and thus the car) would barely run. I was a quarter mile from home...