Dodge Repair: runs great in warm weather, but runs like it is out of time in cold weather.

Question
Got a 2000 Dodge Durango. Last Spring the head gaskets were changed after it had been sitting for a couple of years. Started it up, it ran a little ruff and dieseling when you shut it off as if it was the timing. Checked the timing, the timing was fine. Spring turned to summer and the Durango ran great all summer. Now that the cold weather is here again, it is running ruff and dieseling when you shut it off. It runs great when it is warm, but runs like the timing is bad when it is cold. I think it is a sensor but don't know what one. Any help would be appreciated.

Answer
Hi Ray,
The best way to diagnose this is to take advantage of the built-in diagnostic capability. I don't have an '00 Durango manual, but many of the vehicles of that time-frame can tell you if they have detected a sensor problem by using the ignition key, Turn it "on-off-on-off-on and leave on" doing that in 5 seconds or less elapsed time. Then watch the odometer window in the cluster to see if the mileage reading is replaced by a four digit number preceded by a P.
If that doesn't work then there is a socket under the dash into which a fault code reader is plugged to get that four digit number. A nationwide auto parts store (e.g. Autozone) will often do that for free or an independent shop may charge around $40.
Anyway that you get the number(s) let me know what they are and we'll go from there. Tell me which size (L) engine you have.
Roland