My 07 GT isn't my daily driver so sometimes it sits for a week at a time. After that point, after a cold start up only I'll get just a puff of blue/white smoke on inital start up. Is this ok? What is it?

 

Probably a little oil or gas leakdown into the cylinders. If it sits for a week and only does it sometimes, I wouldn't worry about it.

 

Mine does it on Saturday morning too after sitting all week. I talked to my dealer and he mentioned the same thing as above.

 

Ok, great. Yeah it only does it if I let it sit for a week or so.

 

This past weekend I started the car to fill up the tank and change the oil before putting her away for the winter. I hadn't started it in about 3 weeks and I noticed the exact same thing for the very first time.

 

Happens to me sometimes as well. My car sits for 1 -3 weeks without being started. Shame, Wish I could drive it more, Mustangs need to be driven.

 

That's just the car's way of telling you to take her out more....

 

Do a search...there are tons of threads on this...

 

lol I know there were, I was just lazy and impatient...a little more on the impatient and worried side to search!

 

I had the same problem but it turned out to be the oil being slightly overfilled.

Check the line that goes from the valve cover to the intake right near the throttle body, mine had oil inside and once I took off the intake tube I could see oil in the throttle body. Just sprayed it all out and it's all good.

Check that out first, easy enough to do. Besides that take it in for service at the dealer I would imagine your warranty is still in effect.