Started my car yesterday afterwook (50 degrees outside, clear sky, etc.) and got a momentary metal to metal slipping sound.
Turned it off immediatly, started it again with no problem. Drove home just fine with no power loss etc.

Anyone have any ideas what happened?

 

common on 3 valve motors but mostly on f-150's only seen a few on mustangs nothing you can do it just happens. usually happens after an oil change but i guess you are special.

 

Dont the F150s and our v6 mustangs share a fairly common engine with each other?
What is the noise exactly?

 

No, the V6 Mustang has the 4.0 motor. I think it's the same motor as the Ranger. The F150's have the 4.6 (like the Mustang GT) and the 5.4. They do not have a 4.0 for an F150. They use to have a 4.2 for the V6 F150.

 

That last post is correct. The V6 in the F150 is a 4.2 L and is a completely different beast. It's actually based on the V8 MOD engine. The 4.0 L V6 used in the Mustang is virtually identical to the 4.0 L V6 used in the Ranger. In the Ranger it is rated at 3 hp less because the air box used in the Ranger isn't quite as good. Otherwise it's the identical motor.
I had this noise also. It did it intermitently shortly after I got my Mustang GT. It did it on and off for about 2 weeks and disspaeared as mysteriously as it came. While it was doing it I listend to the various accesories with my stethoscpe and detected a little noise in the belt tensioner. Ford dealer agreed and replaced the tensioner. A day later the noise came back! It did a few more times and stopped. Hasn't done it since. I'm not sure what to make of it other than something possibly wearing "in" on a new car. It hasn't done it now for over two months so I'm not too worried about it though.

 

I had the same problem also, when I started my stang, it made an ugly *** noise. Like a grind, but it didn't sound internal.I too turned it off right away then it started just fine. What I found that fixed the problem was to turn the key 3/4 of the way, then wait like 3-5 secs and then turn on.