Hi,
When this happens, does it seem like you turn the key off, or does it run rough and then slowly stall? Does the engine idle speed maintain around 700 rpms?
There could be a few things causing this kind of issue. First, something as simple as an engine vacuum leak can cause it. Also, a dirty or faulty idle air control valve can do the same. The IAC is responsible for maintaining the engine's idle speed. Actually, Hyundai refers to it as an Idle speed actuator (ISA). It is located on the throttle body. See pic 1 below.
Here is what I suggest: First, check for vacuum leaks. Here is a link showing how it's done:
https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge
If nothing is found, consider servicing the ISA. Here is a link that explains how to service one:
https://www.2carpros.com/articles/idle-air-control-valve-service
Let me know if you have ever noticed black smoke from the exhaust as well. Also, tell me how it runs off idle. If possible, record what it's doing so I can see and hear it. That may help me.
Take care,
Joe
See pic below.
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Thursday, February 10th, 2022 AT 6:28 PM