Tachometer Variance
WARNING: This page is about a different car, the 1996 Mazda Millenia and 1995 Mazda Millenia. However, it is still accessible from the selected car via links, so may be relevant.
Connect positive lead of test tachometer to negative terminal of ignition coil. Connect negative lead of test tachometer to ground. Start engine. Compare vehicle tachometer with test tachometer. Vehicle tachometer performance is acceptable if specification is within allowable range. See TACHOMETER VARIATION SPECIFICATIONS . If tachometer performance is not within specifications, replace tachometer.