RE: Scary Experience
Is it actually accelerating or is it just a drop in braking that gives the impression of acceleration?
The reason I ask is that what you describe sounds very very similar to the Prius braking anomaly that caused all the recalls in early 2010. That seemed to happen on wet, damp roads or wet grate covers etc. It was hard but not impossible to replicate for the dealers and eventually it turned out to be the transition between regen and friction brakes in a situation when the ABS kicks in. If the car was on regen only braking (as the original programming allowed regen only braking in certain circumstances above 7 mph) and the ABS kicked in because of a slippery road etc, there was a hesitation/gap/surge between regen being switched off and the friction brakes having to suddenly 'wake up' or engage. This transition has been measured in the milliseconds but is still noticed by the occupant and feels like a surge. Engineers on the Priuschat forum showed charts with accelerometers etc that there is no acceleration, despite it feeling very much like that; just a flat spot in deceleration.
Since all that trouble the braking has been reprogrammed to allow an element of friction braking and regen at all times (other than below 7 mph where it is friction only), so that if there is a slippery moment the friction brakes are there to take over much quicker. The down side of this is that the Prius now uses it's brake pads at the same rate as a traditional car (almost). It has been a significant balancing act and has resulted in a number of software updates to make it much more acceptable/smoother.
I wonder if something similar is happening with the Fluence? I wonder if you're being gentle on braking and just using regen that when the ABS kicks in (esp now in winter with wet roads) you experience the surge as reported above. When lead footed dealers mechanic stomps on the brakes, they can't reproduce it as the car is immediately using friction brakes and regen?
I could be on the wrong track but it does seem very similar to the Prius issues. Obviously if this is the case it could be totally new to Renault, whereas Toyota have had 5 years to investigate.
Just a thought?