It has the 4.2L V6 in it. It's gettin a little cooler down here in Texas and every year, without fail, my truck starts coughing on every cold start. Gets worse as it gets colder. It always fires up quick, but it sounds like it's down a cylinder for maybe 10-15 seconds. Once its warmed up it runs like a top. It doesn't really happen at all during summer here. What should I be looking for under the hood? Is there a cold start valve of some kind on this engine?

Charlie

 

Just for starters, Your vehicle has a coolant temp sensor that may not be off value enough to set a code , but enough to affect cold start performance.
There is also an air intake temp sensor that could be possibly doing the same thing.
If either of these two are off spec that could very well be some of the problem.
There may be other causes that react to temp and affect cold start performance, but right now I can't think of them.

 

May want to try cleaning the IAC, too.