Please help! tach troubles?
 

I've looked around the site a little, but can't seem to find much. Can't figure out where I put my manual either, otherwise I would have checked it, but....

My tach is acting up. It sometimes works fine, but when it doesn't it misbehaves in one of two ways... (truck is '88 4runner, 22re 5speed)

-totally misbehaving: erratic needle wandering, bouncing anywhere from 0-redline numbers regardless of throttle
-kinda misbehaving: erratic needle wandering during off-throttle (coasting)

Could this simply be a loose wire? My initial thought was a sending unit, but with no manual at the time to help me diagnose, I guess it could be the tach itself. Thoughts? Best way to troubleshoot this? I'm not sure if the tach/sending unit can be tested, and I'm a beginner when it comes to using my multimeter.

Thanks!

-Chris

Sometimes bad plugs,wires,cap or rotor can cause this.Or the ignitor.More than likely it's the tach itself.
Bigblock

I guess I should add that it engine performance doesn't seem to be affected at all (no reliable tach to look at, but...). I found a few posts about high idles and surges, but it's not really the engine. I just put new plugs/cap/rotor in about 5k ago, but not wires.

I had a tach quit all together but it didn't act a fool first.
Bigblock

i cant figure out how to mount my tach there is no coil post to connect it to. any advice would be great.