So, have a few issues related to idle.

When the car is completely off, like it is now, the tach reads 800rpm.

If I start it up, with -everything- in the car set to absolute minimum (That screw at the top of the throttle body, screw at passenger strut, etc.), it still reads 1300ish rpm but turning on any electrical load can almost kill it - it's touchy.

Is the tach being "stuck" at 800rpm minimum - even while off - reflective of anything? Getting idle set is a nightmare, no matter what I do I cannot get the idle to drop under about 1200-1300rpm.

 

take the lens cover off, and push the needle back to 0 haha.

Thats what I do

 

Does that correct incorrect readings, or has the tach simply gone bad?

 

hm... hailing hailers!!

 

Does this change at all if the battery is disconnected too?

Because it's idling at 500 RPM.

The tach is FUBAR, try another.
Quick responding gauges (like speedo and tach) have very delicate mechanisms and really can't be toyed with- your chances of successfully fixing it are about nil.

If the needle doesn't drop to zero when the gauge is disconnected- which would indicate some sort of electrical problem- then you most likely have a mechanical problem with the gauge itself and replacement is the easiest solution.

 

I disconnected the battery, nothing changed on the tach reading.

This would make sense of a lot of problems I've been having ><


Will do, thank you. I assume disconnecting the battery = gauge disconnected?

 

The tach and the gauges are all powered from the row of fuses (bus) called IG1. That bus is only powered if the key is to ON or better. So putting the key to OFF keeps power off the IG1 bus and the gauges etc on IG1.

So you don't have to remove the batt cable to de-energize the tach gauge or the other gauges. Gauge is shot. Did it EVER work right? Since YOU owned it?

 

I do not believe it did work right in the entire time since I owned it.

What could be a potential cause of the issue that I could check for before I drop in a new tach?

 

If the tach goes up and down like it's supposed to, but it's just reading wrong, the needle may have turned relative to the shaft in the gauge. If that's the problem, dkwasherexd is right, just push it so it lines up right. Rev the engine up and check if the tach is reading 6800 when the buzzer comes on. If not, that will show you how far the tach needle needs to turn to be correct.

 

Someone having the face off the cluster and messing around with the needle. Instrument clusters were pretty cheap a couple yrs ago. Maybe thirty bucks or so. The whole thing, not just the tach.

 

If the needle is loose enough to misalign one time, what's to stop it from doing it again?

 

Just checked the tach today when I headed out to replace the instrument cluster, and it is now reading 0rpm while off.

Does this imply a wiring/electrical problem?

 

Needle isn't stuck to the shaft. They are not acting as ONE unit.

 

Aka issue is in the meter, replace the cluster Hailers?

(Edit) After driving it today and paying attention to the idle...

The idle was measured all the fark over the place. There's no way it's idling at 1100rpm during one period, then 1800rpm the next.

 

The needle seems to be somewhat accurate at high rpms, but it is apparently highly inaccurate at lower.

Could this be an electrical issue, or simply tach went bad and replace?

 

If the key was off and the needle was at some rpm as you stated earlier (no power going to the tach in any way if that's the case, then that indicates the tach needle is not attached to it's post good or the tach internals are no darn good imho. I'd try another stock tach myself.

Combination meters used to be fairly cheap a couple yrs ago at the junkyard. Just make sure it's the same series car if you get one like that.

Again, no battery power goes to the tach/instruments if the key is OFF.

 

Welllllllllllllllllllllllllll, actually it could be the needle is TOUCHING something down in the lower rpm ranges and not touching that item in the upper rpm ranges. The only thing it could touch is the back ground that has the numbers on it if memory serves. So you might look really good to see if the needle is bent a bit or ???? or if the needle is touching something when the key is off.

IF the needle hangs up or some rpm with the key OFF, the smack the clear cover on the instrument cluster and see if the needle now drops down. Hard to say from this side of the computer screen.