E420 accelerates then stalls

In a traffic snarl for about 30 minutes, engine running a bit hot 100c. I turned off the a/c to cool it down. When I was slowing down the engine
seemed to accelerate on its own (like a little spurt of gas) then a few seconds later it stalled. I was able to immediately restart. At this point the car seemed to run a little rough. About 20 minutes later it did the same after I filled up with gas. Drove another 200 miles and everything seemed to be fine.
What's up? Any ideas?
Tim Trottier

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