[LMP]

You did not mention engine type....
If that is a 3.1, then I suspect the "trade mark" piston skirt slack these engine are known to exhibit...same as early 3.0 Taurus I had the displeasure to own.. I remember mine had started after a very cold start...
If that is the case, it has no direct consequence..except being really annoying. A short time after starting to show though, this noise would be heard even cold...
I'd like "sounds" to be posted in the same way we post pictures: most digital camera have a sound recording facility and the sound file can be extracted easily.
Come back with more details...