Wacky Tachometer

[steveoelo]

My 90 ranger with the 2.9 has a weird issue, the tach sometimes reads well over what the actual rpm is. It's defiantly a connection but where would I look? The coil has several wires coming out of it

 

[steveoelo]

UPDATE if anyone has this problem, make sure all of your plug wires are making good contact with the distributor. Pushed all of the wires down and hasn't done it since

 

[RonD]

Tach signal comes from TFI module, but is essentially like other older tachs which get signal from Coils "-" post.
On the TFI tach wire is spliced into that wire, coils "-".