My stock 6.0 has for the last 2 years when the cool weather hits and it’s a cold start a rough idle and will almost die if I try to drive before before letting it warm up. I just lived with it until a coworker said his 5.3 truck is doing the same thing. With no check engine lights, besides the IAT sensor I’m not sure where to begin. Anyone else had these issues?

 

Check all your baseline readings with the engine at its coldest,,
If any of the sensors are getting old they often lose the bottom
end of the scale first or drift all the way across either of which may
go away after the engine warms up.

IAT/TPS/CPS/Oil temp/MAF/MAP

 

The culprit might’ve came to light. 1st day of cold (26*) weather truck cranked in the morning but didn’t start. Didn’t troubleshoot but it spun over fast and didn’t hit a lick. So, I took another car to work. After work it’s 46* and truck cranks, spits and sputters. Clears up and cranks fine the rest of the day.

2nd cold morning, cranks but no start. Spins over fast, I can hear the fuel relay clicking but no pump. Jumpered around relay and pump runs and truck starts. I jammed a newer relay in and it started this morning. I’ve never heard of cold killing relays so maybe it was just getting weak.

 

Hey, relays can and do get old. Sorta like us....