I had the same issue of a WiFi Enabled OBD2 plug killing my engine. It was one that was advertised to work with the Apple iOS. There is a thread in here about similar experiences.My 99' 7.3 truck will shut off also when hooked up to my scan tool and will not start until I unplug it from the obd port. One time it ran for about 6 miles before it died on me (using a ELM327 wi-fi reader with Dash Command app on my iPhone)making a left hand turn on a busy highway. I unplugged it and it started right up. I won't try it again in my truck for safety reasons. Both scanners work great on my other vehicles.
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