So, update on this. I don't know if it was the weather, or the engine not quite warmed up or what, but it hasn't quit. I took the belts off and ran it, but it still sounds the same. I'm totally stumped on this. No drivability issues, no drop in rpms, just this kind of popping sound. I had a Volvo that made a sound kind of like this, but only when turning at low speeds and that turned out to be a motor mount. Does this seem likely? Other than that, it has to be internal engine, but it runs perfectly and doesn't seem loud enough or constant enough for that.
