The weather is changing (surprise!) here on the East Coast. This morning, the air temperature was about 52 degrees when I started the car. My vehicle idled surprisingly rough, and for the first 4 or so miles ran like it wanted to stall everytime I came to a stop. The tachometer was right there on 750-800, yet every time I stopped at a light it would idle smooth, and then the tach would drop to maybe 550-600 for a second and then back up to 700 or so. When it dropped you could feel the engine shudder just for the second or so, and then back up to smooth idle at 800. I drove it to public transportation and left it in a covered parking lot. This evening, I started it and it felt similar to how it was this morning. I drove about 20 miles or so, and when I came off the highway it was idling so smooth I thought the engine had cut off. However the tachometer still dropped occasionally to 600 or so for about a second every, say, 15 seconds. The air temperature of course had risen to about 75. I recently cleaned IAC (with brake cleaner, used about a whole can over about a hour of cleaning and shaking the fluid inside the valve), rebuilt distributor, distributor cap is about 6 months old, wires are from PO (I have some to replace them), plugs are about 6 months old. Any ideas why the rough idle in the cold morning, and the engine has this only occasional "miss" in it?