Hi, I just recently bought a 88 LX mustang to replace my recently destroyed vehicle ( live in southern ms, hurricane katrina wasn't very nice to my truck lol ). I paid 850 for the car from a family that is moving away soon, the car was donated to them from Indiana after the storm so I know it's not storm damaged. Anyways on to the problem at hand. When the car cranks up it starts idling up and down fluctuating between about 600 and 1200 rpms before smoothing out. I tried to adjust the idle screw? and raise the idle speed and that helped a bit, but now instead of fluctuating it stays at about 1400 rpms for a few seconds then goes down to about 800 and it idles constant until I turn it off and crank it up again. I've also noticed the voltmeter is rather low, somewhere around 9.5 to 10.5 volts and when I turn on the air conditioner it goes even lower, the headlights dim a little, and the engine loses MASSIVE amounts of power ( think flooring it and going 20mph ).The car had a supposedly "new" altenator on it when I bought it. I've replaced the battery, wires, plugs, dist. cap and rotor button, and fuel and air filters, and still no change. What else could be going on here? Any ideas are greatly appreciated. Thanks !!!