electrical problems, need help

[MaxPlusTen]

well maybe you guys can help me out here... cars been running fine until just recently. I kicked on my a/c for the first time this year and it knocked my voltage down to about 11-12 volts and boged the whole car and gave it a miss at idle.... about a week before the car threw a P0300 Random Multiple Cylinder Missfire (dunno if thats related or just a stupid quenceadence) but at any rate i cleared it and it went away with no return... Now everytime i turn on the a/c though the voltage drags down and it will miss... i have 3 ideas... first and obvious, i think my altenator may be about to take a dump (i also had a battery crap out about a month before this). Second someone told me theres a sensor that has something to do with rather the compressor increases the alternator output while the a/c is on. and my third and most feared is my opti is gonna take a dump on me here soon... anyone that can help would be greatly appriecieated

[Chad97z]

I wouldnt think 11 to 12 volts is dangerously low. The alternator should have a built in regulator. You could have the system checked at walmart. But a slow idle(500rpm) will slow the alternator and decrease voltage. So the question is why is your idle dropping under a load and not remaining constant at or around 750 rpm.

Your IAC valve controls idle speed. When the engine comes under a load, it should pick up the rpm back to normal, which is around 750 or so. Has anyone tampered with your base idle screw? How does the car idle when its cold and hot? Anything unusual? Have you tried cleaning the IAC?

But low voltage shouldnt cause your car to misfire. I had a misfire once due to a malfunctioning injector and once because of a rocker arm that I tightened down too hard. Btw, a slight misfire is more noticeable at lower RPM. So you could possibly have a sticky injector and it becomes more noticable at a lower RPM. I figured out which injector of mine was not working by using a stethescope and listening for the ticking sound on each injector. You should have a constant ticking sound, not random, from each injector.