I have a 1996 Ram 5.2 with 66,000 miles. I bought the truck this past summer and drives great, but the cold months I’ve noticed if I don’t let the truck warm up it will idle fine for a few minutes and then it drops to 500 rpm’s and jump to 1000 until the temp gauge moves. Once that happens it idles smooth again and doesn’t give any problems. It doesn’t do this in the summer. Any help would be appreciated

 

Might be a failing coolant temp sensor. Unfortunately for me, I would need more info to help you. Which would involve a scan tool.