cold start knock

I have a 2003 tacoma prerunner trd. I have a engine knock ( sounds like rod knock ) when i start my truck when its cold and only when it sits over night, it only does it once a day, i can start it and go to work and 11 hours later wont knock on start up. only does it over night and cold out side. it is a loud knock. I have been reading some of the threads on this site , it is not a rattle from air tube or a pully. it sounds like the lower end of engine.
the 3.4L runs great, I never had this noise before. i bought my truck new and it started this when it hit 79,000 miles. Any thoughts on where to look ?

 

Sticking lifter maybe

 

No, Not the lifter's , it sounds like a rod knock, deeper tone than a lifter.
I put in my garage yesturday becuase of the snow and ice we were getting , I still had ice on my truck in the garage and started it and really
didnt do it that much, this time barely heard it, But like i said, it doesnt do it when its warm out,

My head hurts from scratching it so hard !!!

 

Mine just started his winter and I have 230k on it I switched to 5w30 right before it started. It sounds like it coming from a passenger side cylinder and my CEL came on the other day and I've read where someone replaced a coil pack and the sounds stopped. If that will work I think what might be happening is we're getting a week spark on a cylinder from the coil pack and it not creating the needed compression and the piston is tapping. Mine sounds like a woodpecker. When I stopped in teh repair shop the retired owner was walking in and I said EDGAR is it bad when your engine sounds like there is a woodpecker in it?he said Doesn't sound good...paused and said "and it not even woodpecker season yet"
I'm going to buy a coil tomorrow and replace it on cylinder 3 and see if it helps.