My tachometer just started acting up. It acts like it's sticking but it's not. The needle jumps up and down occasionally. If I'm cruising at 2500 RPM, sometime's it'll jump to 3000 and then back to 2500... or the opposite will happen, it'll jump down to 2000 and then back up to 2500. Sometimes it sticks... again, if I'm cruising at 2500 RPM and slowly start to slow down, the needle will stay at 2500 and suddenly drop down to the right RPM.

I don't think it's a physical rubbing/sticking problem... it acts like an electrical problem. Engine runs fine, no MIL.

Gauges are original, no mods other than a SuperChip which has been installed for over two years.

Is there an easy way to determine if it's the gauge or the PCM?

 

I have 1996 F-150 XLT and it appears to be doing a similar action. It seems fine at lower rpm's and at very steady highway driving. But during highway driving it tends to either stick around 2500 rpm's ( where it outta be ) or kinda bounce like crazy between 2500 rpm's and 3000. The truck appears to be running fine, but still a worry.

Any other posts would be helpful.

 

I put my AutoXRay on the ODB II port and monitored the engine RPM's as reported by the PCM. Everything looks fine. So, my problem seems to be a bad tach.