Welcome to 2CarPros.
That is a tough one because it is so random. However, for it to happen, my guess is it is either a fuel or ignition related issue. Have you ever noticed any other symptoms? For example, does it only happen when the engine is cold or only when climbing a hill?
The reason I ask is because if you have a weak fuel pump or partially plugged fuel filter, going up a steep hill will require more fuel which if restricted can cause the engine to stall. On the other hand, if it only happens when the engine is hot, it could be a crankshaft position sensor starting to go bad because they become very sensitive to heat.
Take a look through these links. The crank sensor under certain conditions, won't even set the check engine light to come on.
https://www.2carpros.com/articles/how-a-crank-shaft-angle-sensor-works
https://www.2carpros.com/articles/symptoms-of-a-bad-crankshaft-sensor
Here is a link that shows how in general one is replaced:
https://www.2carpros.com/articles/crankshaft-angle-sensor-replacement
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Next, you mentioned about the fuel level. It is unlikely that having a half tank of fuel would cause an issue, but one never knows. In this case, I would recommend testing fuel pump pressure to confirm it is within the manufacturer's specs. Here is a link showing how it is done. Note: A fuel pressure gauge is needed. Most parts stores will lend or rent one to you.
https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator
Please understand, on today's cars, we have become very dependent on computers. If the check engine light comes on, it will point us in the right direction. If it doesn't, then we have to try and diagnose the issue blindly. This could even be as simple as needing a new fuel filter. It's hard to tell.
If, however, the check engine light is on when the engine is running, then you need to have the computer scanned for diagnostic trouble codes. If you get any, let me know what they are. It will make trouble shooting much easier.
Take care and let me know if you have other questions.
Joe
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Tuesday, August 13th, 2019 AT 8:08 PM