OK it's 20 deg F out never had this happen and its been pretty chilily out. I started the car and cranked for a little longer than usual, then once it fired up I heard a loud KER -KLUNK, KER- KLUNK, Ker-KLUNK knock from under hood did it three times then stopped. It almost sounded like something was stuck? The engine was just fired and running when it did it , right when it fired. Only did 3 times then nothing. This is the coldest it's been. I have no known problems just had fully engine checked with diagnostics and everything from jag

 

Josh, the clunks are likely the initial cycling of the a/c compressor during cold temps. Low temps. will cause the charge to contract or condence. Shut off a/c, let her get dead cold, then start her up to test...

 

A/c? I'm doubtful.