I have read somewhere that the factory tach does not always read correctly.
I hooked up a scan tool and the RPM is right around 800 at idle when warm which I believe should be about right but my dash tach reads 1100.
Is there a way to adjust the dash tach to read correctly?

 

Are we talking about the ‘97 Z28 shown in your avatar?

 

Yes

 

Any suggestions on this issue?

 

I’ve found them to be 100-200 RPM off. 300 RPM seems excessive. And 800 RPM is the stock program idle speed for the M6, engine warmed up (actually, 111°F and above).

Using your scan tool check PCM RPM vs tach RPM over a wide range of RPM. See if the error is a constant, a percentage, or random value. If it's a constant might be able to reset (move) the needle on the tach. Is there possibly an “overlay” on the cluster that required removing the instrument needles to install?

 

Thanks Injuneer
I will look at that.
No overlay.
Car is completely stock.
Has only 27K kilometers on it (17K miles)

 

White cluster overlays were all the fad back in the 90’s. Fortunately your low mileage 97 escaped unscathed……

 

IP Address 2409:4055:4e0f:5050:4d56:3b2a:e430:70d3 % Abuse contact for '2409:4000::/22' is ''

inet6num: 2409:4000::/22
netname: RELIANCEJIO-IN
descr: Reliance Jio Infocomm Limited
country: IN
org: ORG-RJIL1-AP
admin-c: RJIL1-AP
tech-c: RJIL1-AP
abuse-c: AR991-AP
status: ALLOCATED PORTABLE
remarks: --------------------------------------------------------
remarks: To report network abuse, please contact mnt-irt
remarks: For troubleshooting, please contact tech-c and admin-c
remarks: Report invalid contact via www.apnic.net/invalidcontact
remarks: --------------------------------------------------------

 

Was wondering what that was all about.

 

They’ve opened maybe 50 fake accounts over the past few years. Almost all the IP addresses trace to India.