I have a 87 5 speed with 4cy and a DIS, the car has been sitting for 2 years and i just got it running today! YAY me.. Every thing was working fine then the tach just stopped working, so i turned the car off and turn the key back on and i see the the tack move a slight bit, so i continue to start the car still no tach. I done some reading on the forum and have seen people talking about the tach filter, most people are saying that the 87 and 88 don't have them. I have tried smacking the top of the dash to see if it would start working again , but nothing. any ideas?

Something in dash wiring is bad/loose or tach itself is bad.

DIS doesn't use a tach filter.
See my cave, DIS in 4 cyl engine section.

Be careful dealing w/ dash flex board. Likes to loose or gets bend traces at plug because "glue" goes bad.

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave (It's also at the top and bottom of every forum page...)