Hello, just purchased a really nice 1990 Dodge Dakota convertible, this makes the 8th one I've had. Love these things. However, this one has a strange problem I hadn't run into before. 3.9 V-6 Automatic/ 4x4 all options, the tach jumps back and forth or up and down, or however you want to describe it, makeing it impossible to calculate what it is actually registering. Anybody had this problem that can lead me into a starting point for my search. I would guess it's a ground problem, but thought somone else out there might be able to identify a good starting place to look. Thanks

 

I have the same thing with my 90. Was jumping around for a while now just goes to 1500 and stays there. I was hoping someone would give us some clue. I did take the tac out and clean the eletrical connectors no help.

 

Mine seems to be registering approx double the actual RPM, if that helps anyone with trouble shooting. But really jumps around alot. Thanks