Having some power issues going on and work has me tied up. I'm looking to spitball some solutions.

Problem:

Car has been sluggish lately. No codes. IAM is 16. Once in awhile the car will have a sudden power increase. Engine is quieter, much easier to take off from a stop, radio volume increases without knob adjustment, power steering more responsive. At idle I could barely tell the engine was on. After a few miles it goes back to running a little crappier. Usually a bump or a turn will cause the issue to come and go.

Voltage Readings @ Optima Red Battery Terminals:

Engine OFF: 13.3VDC
Engine ON @ Idle (No load): 14.4VDC
Engine ON @ Idle (Brights, Full Blower, Rear Windows Defrost): 12.15VDC
Engine ON @ Idle (Brights, Full Blowers, Rear Windows Defrost, A/C On): 11.85VDC

-Accessory belt is tight, replaced about 2K miles ago
-Battery is 1 year old (Optima Red Top)
-Checked engine grounds. All within about 1 ohm of each other.

I'm DC amp probing the alternator over my lunch break, but that's all I have time for at the moment. The kid I bought the car from had a huge amp in the car based on the wiring I found. I'm assuming the alternator is on it's way out.

Any other suggestions? Has anyone experienced something like this before?

Edit: Also noticed that when just headlights are flipped on my engine vacuum drops from -10.15 PSI to -8.70 PSI. Roughly a 15% decrease in vacuum. Sounds more and more like the alternator...

It sounds like some of the diodes are bad in the alternator. It can't handle the high load. You could remove the alternator and have it checked out at Autozone. I think they will verify that it is bad.

Update:

Cleaned every ground I could find. Scrubbed each bolt, washer, surface, and wire end with a wire brush. When I ohm the grounds to the battery I'm now getting no higher than 0.1 ohms (whereas before the highest point was 1.1 ohms).

Car runs much better, smoother, and my steering is more responsive.

Thank god...

Very good idea and great results. Make sure that the alternator voltage stays above 12.5 volts while the lights and blower are working on high and the engine is running around 2,000 RPM. If that checks out then you should be good to go. Also make sure the alternator belt is snug.