Martin , I also have a 97 4.6 liter .
Last year I changed the ignition coil for a pertronix coil to match the pertronix distributor. Car ran great but the tach read 1/2 engine speed , no amount of checking wiring and even running separate wires from coil to tach would change things so I changed the dip switches which you will find on the back of the tach to the 4 cyl setting and my tach is now ( approximately) correct ?
Made no sence at all .
Perhaps pop the tach out and move the switches around the clean the contacts ?
BTW if anyone has a used tach for sale I would be interested 😊
Cheers Dave
