Tach Reading High and still climbing

[vortex2450]

My tach is having a weird fit. It is now reading about 1350rpms higher than it should (~2k @ idle). it started 3 days ago. I turned the key on and the tach jumped to 300rpm with the engine off and stayed there, making it 300 rpm fast, then it jumped to 500rpm fast, and then 800 rpm fast, and then 1200, rpm fast and so forth to it is now way off.

I recently pulled my dash apart and because I bumped both the speedo and tach needle out of place I pulled them off with a fork and put them back on until my speedo was dead on with a gps and my idle rpm sat perfectly @ 800rpm. That was a week ago. It was reading perfect until this issue started...

When I cut the car off and leave the key in the "On" position is reads 1350rpm now.. I seems that almost everytime i turn the car on/off the reading gets further and further off. It reads fine in respect to engine speed and doesn't bounce or jump or get stuck, it's just reading higher and higher off the mark...

Any ideas here? Did i screw something up?


Thanks,
josh

 

[frosho]

I wonder if the needle might be a little loose. I've never removed a one, so I'm not sure how they're attached. I assume they're a press fit... yes? Maybe it needs to be pressed on with a little more force.

 

[Bob Gervais]

Crank cancer.