What would suddenly make my tachometer go crazy?

[thkfast]

I own a 1993 FJ1200 ABS (17,000 miles on it) and all of a sudden the tachometer started reading WAY high!  At idle, it shows 3,000 rpms and cruising along at around 45 mph, it's way into REDLINE!  I was curious if the engine would cut out at an indicated 11,000 rpms so I went 55 or 60 mph in a lower gear...it doesn't cut out, so the engine must not think it's grenading!  Any experts out there know what's going on?  Thank you!

EDIT: Obviously I'm new...this has been covered before - SORRY! - I'm going to check the ground on my coils.

[Dan Filetti]

Yet again, the crazy tach issue.  The running theory is apparently that the ground is weak.  I'd love to read that this has been resolved by someone that completely cleaned up and re-grounded the coils.

Anyone, with actual experience, please chime in.

Dan

[SlowOldGuy]

A loose "pickup" wire (or bad connection) could cause the tach to think it was seeing many more firing events that were actually happening.  The coils are grounded through the ignition unit, that's what makes them fire. 

DavidR.

[thkfast]

Slow Old Guy,

I'm double dipping in two threads on this problem - also over at RUNNING PROBLEMS.  I have little to no
mechanical knowledge - I've cleaned up and tightened the ground at the coils but the tach is still
showing WAY TOO HIGH!  I have photos posted on that thread if you could direct me what to
try next?  

Thank you.