Tachometer malfunction!

[prophetickai]

I looked and couldn't find anyone with a similar issue. I know my car has been rigged majorly before I bought it as far as wiring goes, so I'm going to assume its in the jumble of wires that don't belong. My problem has only happened once so far while accelerating to get out of my driveway. My rpms dropped, car ran a little like an injector clogged for a second, and my rpms were registering at a little over 1.5k even though it should've been showing around 4.5 to 5k. It stayed there for about 2-3 min even throughout gear changes as I searched for somewhere to pull over (I live on a busy highway) then magically went back to the proper reading. The irregular fuel feeling is kind of normal because my O2 sensor is still pulling a code even though I just replaced it. Any ideas as to why my tach decided to drop and not stop working all together? I've had my Z32 for a while and it's never done that before. It's ran fine since and it's been a few days since it happened.

[Ace2cool]

Oh man, sorry I didn't see this till just now.

The EL section of the FSM would be the only place I would think to check. It could be a dirty/corroded connection in the back of the cluster. If that's not it, the gauge itself is most likely on its way out.

And as far as the O2 sensor, did you use an OEM replacement or a cheapo auto parts store one?