Early January I realized the hard way I forgot to keep up on the antifreeze mixture. The cars a 90 4 door GS with 178K miles on it. Still runs strong and gets ragged everyday. The waterpump broke trying to grind through the ice and started leaking coolant. Thinking it was more like a cracked block or freeze plug I tried to drive it and get it looked at, of course it slightly overheated which I'd turn it off and coast every opportunity. Waterpump is now fixed but the idle was really bad up and down and usually die. Thinking maybe the ice F'd up the Idle Air Control valve I replaced it with one I saved from my last car. It doesn't quite die now but really tries sometimes. It doesn't do it when cold (since it's idled up) and once it's driven for awhile 20-30 minutes it will hold a decent but rought idle for a few minutes and then drops down. I think the head gasket has been a little bit of a problem for the last year cause the car uses coolant but no signs of where it goes. Still no signs of contamination in the oil or coolant but I'm thinking maybe the gasket is blown between cylinders. Also I get pinging at about 3-4K RPM's now which never happened before. Any thoughts on this as the idle was always a little rough before but had no problems staying at one set RPM.