There could be a few different reasons why a vehicle would be stalling. Try checking the fuel filter, fuel pump or the injection plug.
Year, Make, Model, engine size please. possibly an ignition or sensor (electronic part).
If you run 6 miles in 20 minutes, then you run 1/6th the mileage (1 mile) in 1/6th the time (1/6 x 20/1) 20/6 = 3 2/6 minutes = 3 1/3 minutes = 3 minutes 20 seconds 1 mile = 3 minutes 20 seconds
idler may be set too low...causing the car to stall out. from a dead stop in a car with an automatic transmission you should be able to let off the brakes and the car will accelerate on it's own (without you stepping on the gas) to at least 10 mph if not closer to 20 mph.
2.33 miles in 20 minutes at 7.0 mph
The fan motor my be out. Open hood let car run for a few minutes and see if your fans come on if not my be the problem.
going that slow for a certain amount of time will cause it to stall after 10 minutes it should stop. if not go see your dealer about it:)
check the fuel filter, may be clogged.
I'm not sure if you can walk a mile in 20 minutes but I'm able to run a mile in 10 minutes.
2.33
20 minutes
If a car travels for 20 minutes at a speed of 60 miles per hour the car travels 20 miles.
If you run 2.5 miles in 20 minutes your average speed is 7.5 miles per hour.