My guess would be the thermoswitch, which is what Alfred5279 is referring to. If you check the timing at full warm idle, and it's correct (matches up w/ red, usually easier to see at night) than it shouldn't be a factor in the overheating. Even if your timing was set at max advance/retard, the car would be able to keep from overheating (at least at idle), assuming the cooling system is working correctly.

If you search for thermoswitch on this forum, you'll find threads with pics of the thermoswitch on your car. I believe the torque is 17ft-lbs. After replacement you'll have to bleed the system, leave the cap at the first stop (not all the way closed) and idle the engine until the cooling fan comes on twice (watching temp. gauge just to be safe). Then add coolant if necessary to the rad. and in a day or two add to the overflow bottle which will be low. - think you already know all that, but in case someone else doesn't...

edit: found the pic, you can thank Civic2Scooby (and the plastic is blue on that one 'cause it's a Spoon, otherwise it's usually brown)

[SPOILER="thermoswitch"][/SPOILER]