AutoMeter Tach is off

[92greenlx]

When I got my car smogged my tach at idle read about 1050 rpm. But the computer to the smog machine read it at 779. HAs anyone ever experienced this? I had always suspected my rpm to be a little off but now I know for sure it is. Think it's time to buy a new tach. My stock tach on the dash sits at 3000rpm and doesnt move much.

 

[HISSIN50]

i would be more likely to suspect the other tach was off, especially since it read low. if it was an inductive tach, they can be not terribly accurate.

 

[stangbear427]

Right. They are only there to give a baseline/consistant reading throughout the steps of the smog test process. However, if you are really sure the tach is off, I'd talk to Autometer. They may have some troubleshooting ideas, or just tell you to send it in. Their customer service is