I have read many other post about the 1997-2003 trucks having this same problem but I don't know that I have seen a exact fix yet. I cleaned my MAF, and IAC, replaced plugs and half of the coils, checked for vacuum leaks and replaced my air filter and fuel filter. I still get a rough idle when it is below 45 degrees outside.

I have read that it could be a manifold problem, has anyone tried new manifolds or gaskets to see if that was it?

Any input would help.

 

I have the same issue on my 2001 with 5.4. I think that I need to clean my Throttle Body again. It has been a while since I've done that (maybe a year and a half). Have you checked the TB?

 

Could be the IAC needs replaced..