Tachometer and engine auto revving

I have just bought my first car. I noticed the tachometer does not work and I was wondering is this is something that is easily fixed (eg, a fuse or something). I also have a problem were the car drives fine and the it starts automatically revving its self. It has happened a couple of times but not every time. The car started off fine then I put the clutch in and put it into neutral (same as any other time) and the car started revving as if I had my foot slightly on the accelerator. I turned the car off and it stopped so I turned it back on and started driving again, but when I stopped at some lights I realized it was still doing it. I only notice it when the clutch is in or in natural (based off sound). If I leave it for a while it seems to go away. It could be something sticking? Ga15 engine.