I've been having a time with my 2001 Sable. I recently changed out the plugs/ wires as the car has 125K miles and the plugs hadn't been changed. The car at idle seems kind of rough and I thought the plugs would improve things, but that didn't happen. I borrowed a friend's cheap code meter and no codes were shown and the readings I saw looked normal, maybe a slightly elevated long term fuel reading but otherwise ok. I also have a '00 Taurus with the same engine, but it at idle is much smoother and there doesn't seem to be much difference in OBD readings.
Any ideas as to the rough idle?