Truck is a '97 4.6 Romeo. The coolant has been leaking for a few months out of what I believe is a port in the firewall on the passengers side connecting to the heater core (but never had any leak inside the cab). Not leaking fast, but more noticeable when I get on the gas (I used to be able to smell it through my vents from time to time). In the past month or so I've noticed the truck idling a little rougher, and a few weeks ago one of the coolant lines connecting to the firewall (the one with the Prestone valve) came off at the firewall, forcing me to lose coolant while driving. I reattached the hose and filled it back up, but I'd like to get to the bottom of the problem so I can fix things before anything else gets messed up.

 

Did you get antifreeze on your plug wires? That will ruin them and possibly cause a rough idle. You can always pressurize the coolant system and find your leak.