James Rouse

Hi guys , I have an 84 US automatic that is my daily driver , the other night I came out of work to find a cold snap had occurred (It was 9 degrees) and when I started my car , which had been running smooth as silk , it was idling very rough when in gear, she idles fine in neutral or park , but when the engine is under a load and the tach drops below about 1100 rpm it starts ....missing, for lack of a better term, I thought it may be a little water in the gas but have since put in a tank of fresh from my regular station and am still seeing this rough idle but not all the time, I've also noticed that my temperature gauge isn't working correctly (sometimes not at all) and that also started on the same night could the two things be related? any help you guys could give would be greatly appreciated !

Mrmerlin

has the green wire ever been replaced?
how about the plug wires?
did you run the engine in the dark and look at the wires for jumping sparks?
What was the last thing you fixed?
do you use a bottle of techron every 3K miles?
do you put MMO into the fuel?