Thank you for the good questions and comments. I will run them by the current mechanic--the first, who are always quite good, gave up and sent us to a "Volvo Whisperer"--although he is still puzzled. What particularly doesn't make much sense is that once it stops, or we turn it off because...

Our V70 starts and runs fine until it gets well warmed--usually about 30 minutes, depending on whether driving city streets or highways. At that point it begins to choke, sputter, and eventually stop completely. It will restart immediately and run a short distance (usually no more than 1/2 mile) bef...