Assuming that the V8 has a similar system as the rest which monitors for belt slippage, this may be the problem. The symptoms you describe match up perfectly with a slipping belt.
Is the belly pan still under the engine?
Did you go through a water puddle?
I went through something like this several weeks back, it cured itself and all was well.
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in