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Hi, my name is*****'s possible that the fuel pump or the fuel pump relay is malfunctioning. You should have the fuel pressure tested and the relay inspected when the car is not starting. It can be difficult to catch an intermittent problem like this in order to do any testing. Ideally a test for spark from the ignition system should also be performed when the car stalls. A faulty fuel pump relay is pretty common for this type of problem. You might try substituting a known good fuel pump relay and see if it solves the problem.
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