RPM gauge behaving oddly

[4bangr]

i've been noticing my RPM gauge will jump up and down (without any additional foot pedel pressure). it seems to work correctly most the time, but sometime it catches my eye when it spikes up to 3500 or so, then it will fall back down after a few seconds.

is that driven from the ECU?

 

[ThorInc]

With a corresponding audible tone or not? Auto or manual?

 

[4bangr]

With a corresponding audible tone or not? Auto or manual?

i haven't noticed any corresponding sound - Automatic

 

[Paperjam]

So the tachometer is spiking and the engine speed is not increasing or is the engine speed increasing and the tachometer is indicating the speed increase? The first will likely be an electrical fault, a short, etc. The second will likely be mechanical, perhaps a vacuum leak.

 

[4bangr]

So the tachometer is spiking and the engine speed is not increasing or is the engine speed increasing and the tachometer is indicating the speed increase? The first will likely be an electrical fault, a short, etc. The second will likely be mechanical, perhaps a vacuum leak.

the engine speed is not increasing.
I'm thinking the gauge is fed from the ECU; I hope it's not an ECU issue, therefore, it might be a connector or maybe the gauge is going bad.

I thought someone might have seen this before.

 

[Paperjam]

There is probably a loose connection or a short to power somewhere. What year is it? 3rz?