I am new to the forum and this is my last resort to get a warranty item corrected on my drive train. I have a 2012 Volt with 86K miles on it. It is a great vehicle and recently I had the driver's side bearing replaced on the car. When I got it back, not sure if it is just a coincidence or not, I noticed the car missing like when you have a bad plug. It would be just a moment when there was a very sudden loss of power in the drive and then it would pick back up very quickly. It never happens when the Volt is on the battery, so I have eliminated the servo drive motor for the vehicle and the battery. Once the battery is depleted and the engine starts to run the generator for the drive motor it occurs. If I attempt to accelerate heavily it will jerk and I will have a very noticeable reduction in power. It very rarely logs a code for diagnostics. Once it logged a code that read Propulsion reduced I think. It is happening both when accelerating as well as coasting to a stop. I have taken it to 3 dealers and they have told me they could not get it to repeat the problem. It is usually 8 to 10 miles into the drive with the motor operating the generator before it happens. Does anyone have any ideas?