Strange Electrical Issue
 

I have a 1989 n/a 300zx and I am having some really odd issues crop up.

Here is a little background story: Last week I began to have an issue with my idle wavering between 300-800 RPMs occasionally. This was most likely to happen when there was some sort of load being put on the car (press the brakes, power steering, etc). Turning the a/c on tended to level the idle out enough to drive the car.

So, over the weekend I replaced the master cylinder because the car was consuming a bit of brake fluid. This seemed to help the issue out slightly, the bouts of idle instability were a bit less intense, though still very noticeable.

A few days ago, the battery in the car died. After replacing it, the idle seemed to smooth out a lot. Though, there are still fits of instability the intensity is much less - it only jumps around about 50-100 RPMS less frequently (I am almost just chalking that up to being the car is old). However, now when I press the brakes the entire radio/a/c display totally cuts out for a fraction of a second. The volt meter also correspondingly moves all the way to the left for the split-second.

I am epicly confused. Any thoughts?