2004 Endeavor LS Cold Start Rattle
 

I have a 2004 Endeavor LS (150000 miles).
-When i start up it makes a pretty loud rattle sound from under the hood (the colder it is the worse the rattle is). As the vehicle warms up it goes away.
-Also if I try to drive it within a minute of first starting it, it is EXTREMELY sluggish, it normally runs great. (I don't even try I assume its not good for the engine).
-When I do start it it runs at 1500 rpm and slowly goes down to about 6'-800, I dont know if that in itself is a problem but no other cars I have driven do that.
-One day I left it out over night in about 20 degree weater and when I started it, it sounded as if was about to quit and die, then it finally started.
-The engine fluids have always been replaced on time, and it has been taken care of.

Any ideas of why it doesn't do well starting in the cold?

very common for 2004 and on v6 galant and endeavor. mitsubishi put out a tech talk article on this a few times. the problem is low quality gasoline leaves ALOT of deposits in your combustion chamber and the after effects seem to come out durring cold weather. carbon builds up so much on the piston it hits the head and that is the noise you hear. piston slap is a common term for it. according to mitsubishi there is 2 ways to get rid of this condition. first of when you crank it up and you hear that noise, rev it up to about 3 grand and let off the gas, repeat this as many times as it takes to break up the carbon. could take as many as 30 times. then you need to have an intake flush done. BG products work great. not an injector flush, INTAKE flush. to prevent this from happening again, use a name brand gasoline, chevron, shell,ect..... if you cant, this will happen again, but just use this countermeasure when it does!! i have used this countermeasure MANY times and have had a 100% success rate.