Diesel running rough when outside temperatures change to cold?

I have seen the engine coolant temperature sensor go out and cause this issue, but can I ask if you have run the codes?

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Here is information I found on the PDM:

The PMD in these engines is known to have issues, primarily due to its original location on the injection pump, where it is exposed to significant heat.

Here is the location of the engine coolant temperature sensor in case you what to swap it out. Check out the images (below). Let us know how it goes

Thanks Ken. I will replace that sensor. I thought I did when I put my turbo gauge on. But I may not have. The computer is not throwing any codes. I did relocate the PMD to a cool place. I thought maybe the injection pump may be going bad. Bud it just doesn't make sense if it runs excellent in the warm weather. Sadly, where I live no one seems to work on 6.5. but one mechanic thought it may need a new injection pump but wasn't sure. Plus, when I open the fuel line it pours right out nicely. Again, thanks for all your help. I will replace the sensor and get back to you.

You are welcome please let me know how it goes. The sensor should fix the problem.

I put a new sensor on it and unfortunately it still runs the same.

I am sorry to hear that, are there any other trouble codes? Also did you change out the fuel filter/water separators? This video will show you how:

https://youtu.be/lEbTuBAULD4?si=aa8qNCW-VqaMJuxE

Please go over this guide and get back to us.

Yes, I have replaced the fuel filter. Just seems so weird that it's 40 degrees and it idles perfectly but the acceleration is either all or nothing. Like somewhere in the middle, it's missing until warmed up. Then you can slowly feel that miss start getting better. But if it is 80degrees it acts like nothing is even wrong with it. With it being a 1996, is there a fuel heater in these trucks that warm up the fuel before the injection pump? Just wondering if that would make sense in only the cold. I did take it in and the guy wasn't for sure but said it was probably the injection pump. But the injection pump pours good fuel out of it and wouldn't make sense that it would get better the longer you drive it. But if it only idols it will still run crappy. It has to be driving around on the hwy for it to start running correctly. I have went hunting and driving it slowly does fine but as soon as I get on the hwy it will have that miss come on and then 20 minutes later it runs perfectly. Thanks again for your help Ken.

Yep, it sounds like the fuel injection pump is going bad, at least we went over everything else first. Here are the instructions on how to change it out. Check out the images (below). Let us know what you find.

should I change the timing chain while I'm in there and put in new fuel injectors in it? Is this a big job? How many hours should I expect? Thanks

If you want to do a timing chain please start new thread we only handle one problem per question. I would install new fuel injectors while you are there, here is how. Check out the images (below). Let us know what you find.