Tach problems
Tach filter is located on top of the intake manifold on drivers side on an 84. Should be similar location on an 85. Looks like a little metal tube wired to the distributor and will shunt voltage spikes and noise to ground before it reaches the tach to prevent damage. It is a discontinued part so you have to home make one or pay a lot for an aftermarket one through CC or Ecklers. There is a guy who sells them on the web named Rodney Dickman http://www.fieros.de/en/articles/tachfilt.html
See the link and google him. I got one from him and it worked great. Good luck. Mike





