tach reading way off?help?

L

lt1sy

Doghouse Member
problem is on a stock v6 TY not lt1 SY in my sig

well it hadn't bugged me since buying the truck, but all of the gauges on the cluster work fine without any issues. except the RPM guage when at idle reads like 1500-2000 rpms and when you drive truck it actually raises with no juming or fluttering nice and smooth just totally OFF it will see redline before trans normally shifts at (4800 stock) I changed all ignition componets and after and before tach still acts the same way.

could this be a ground or something obviously the signal from coil is getting to cluster just reading way more.




also the odometer in my truck doesn't work I did searches to find out that it was a stepper motor that's bad supposedly which causes the ODO to stop marking I have to change that but I noticed that the TRIPOMETER was still marking without issues I was under the impression that bot the ODO and TRIP worked in unison? or am I wrong?

any help on this would be great guys thanks, I did a lot of searching but only found ignition related issues to misfires but no hardcore dash cluster troubleshooting info.
 
Last edited:
Daryl H

Daryl H

Donating Member
Re: tach reading way off?help?

Does the tach read the same amount wrong all thru the range of the engine RPM?

The speedometer/odometer/tripometer all get the same signal.
 
L

lt1sy

Doghouse Member
Re: tach reading way off?help?

Hey daryl yes it appears to be reading wrong the same amount thru rpm, but as i said the odometer and rpm guage are the only ones with issues. The speedometer reads acurately.

Could it be a ground or connection on back of cluster? I just didnt want topull clusterfor no reason.
 
S

Snoman002

New member
Re: tach reading way off?help?

first and foremost you need to verify it against a known quality reference.

Find an autometer tach, or something, that can measure the RPM directly. Heck, walmart rental an Autometer tach, hook it up, veryify the RPM reading against the gauge cluster and then return it as defective.

Then, you need to figure out if its always 500 RPM high, or 10% high. Point being, if at idle its off by 500 RPM and at redline its also off by 500 rpm then its always the same amout and could just be the needle on the gauge itself. But if at and idle of 1000 rpm its reading 1100, and then at 4000 rpm its reading 4400 then its off by 10% and the issue is deeper.

Either way, make sure it actually IS reading high, make sure by how much it reading high, and then see if its the same amout or the same percent. You can't diagnose something that looks like it might be wrong, you need to know first. I knew a guy who bought a muscle car, and then because it ran hot put a new thermostat in, then an electric fan, then a big expensive radiator, only to find out the $5 temp sensor was bad. Never once did he compare a reading off the radiator with the gauge. Had he used an outside, good quality temperature gauge to compare with what his gauge was reading he would have realized the problem right away.
 
L

lt1sy

Doghouse Member
Re: tach reading way off?help?

the gauges is reading way off as you rev cause the needle goes past highest mark which I think is 7k when it shifts, and trans shifts nice and firm and EARLY like you can tell its t the stock 4500-4800 shift point it leaves you wanting more RPM but the guage will mark past 7k cruising it marks 3500rpm I just didn't want to buy a guage for now I was planning on running a scanmaster when I got some extra coin to do so.
 
S

Snoman002

New member
Re: tach reading way off?help?

Then bring it to the parts store and have them hook up their scanners. Most of them can do RPM at least, that should be able to tell you where you are really at when the tach says 1k, 2k and 4k.
 
Daryl H

Daryl H

Donating Member
Re: tach reading way off?help?

Pull the RPM needle off and re-adjust with the engine running. If you take the glass/plastic off of the instrument cluster and reinstall the cluster you can go for a test spin to verify proper orientation of the needle.

The odometer motor has a bad gear in it. They are plastic and go bad. You can swap out the motor portion of the odometer and keep the digit portion. Another small possibility is that the digit portion has some mi-aligned teeth. Wont know till its taken apart.
 
L

lt1sy

Doghouse Member
Re: tach reading way off?help?

ok gotcha daryl quick ? tho are these clusters known for decalibrating the tach ? when nothing has been touched on them? I could understand if they had installed a set of white face gauges improperly but why would a stock guage just decalibrate itself if it hasn't been played with at all?

in order to pull off the needle I need to remove cluster completely from dash?
 
Daryl H

Daryl H

Donating Member
Re: tach reading way off?help?

I have not heard of a tach slipping.
I have taken mine out on numerous occasions for white face gauges, odometer quit working, trip meter quit working, ect....
You will have to completely remove from the vehicle to pull off the glass.
 
You must log in or register to reply here.
Top