Lets me start by saying this car has had ignition problems since I bought it. On the test drive it had a real bad miss around 4500 rpms. I replaced coil, plugs, and wires, which seems to make it dissapear. Then one day I heard a loud pop noise and the car shut down, white smoke from the PCM area. After letting it sit for awhile and a new coil, she fired back up. Then after running it hard it died twice on me, both times voltage dipped way low before shutting off, but it would start right back up with no problem. Now when the car gets warm and I have the rear window defrost on the voltage goes down into the red. I did have to change out the stock defrost fuse for a common fuse...could that have anything to do with it? I had the alternator tested, and that came back fine, and I put in a red top Optima. What could be wrong with the electrical system? Oh btw, car had 50k on it when bought and now has 82k, still on original opti.

Thanks.

 

They all draw too much current. But yours seems worse than most. Perhaps the voltage is dropping so low, the PCM goes into a "brown" condition. At this point until you do some more investigation, we won't know where the problem is. However, you can start eliminating some things from the list.

First I want to say, the optima batteries are a glass mat battery and never use a conventional battery charger if you need to refresh it.

I suggest as far as your electrical system goes, you should check all the grounds and the positive connections as well. The important grounds are the one located on the block by the ICM and the other end where the strap goes to the frame.

There is another ground on the radiator support and another above the starter. Also pay attention to the negative and positive cluster on the passenger fender. What you need to be doing is remove the terminals, make both the terminal and the mounting point clean and shiney and then retighten.

Once they are done, start taking some measurements. With all the accessories turn OFF, start the engine and measure the voltage across the battery. Should read somewhere near 14 volts. Now turn on everything you can think of like: AC, high beams, radio etc..... Now measure the voltage across the battery. Shouldn't dip below 13 volts.

Let us know what you find.

 

ok, heres what I got:

Car off: 12.5v
Car running with nothing on: 14.3v

Now when I turned on all the accessories it was at 13.5v to start with and then my car kinda died and it dropped to 12.5v and then came right back up to 13.1v and then fluctated between 13.3v and 13.1v with the occasinal 12.8v.

I still haven't cleaned or checked any ground posts yet.

 

Not just the grounds. Repeat the tests and let us know.

Do one more thing after you finish the electrical connections. Measure the AC output from the alternator. Put the voltmeter on AC and measure from the negative terminal of the battery to the large output post of the alternator. Again, the meter this time is set for AC. The reading should NOT be higher than 0.03 VAC. If it is higher, that means the diodes are leaking. Time to replace the alternator.