Foxbody Tachometer "Jumpy"

KaLiKo Street · Mar 6, 2012

My 92 that im currently in the middle of doing the 5.0 swap with, has always had a problem with the tachometer either not working or being jumpy. Anyone know why? My old 85mph gauges did it and now a whole newer set of 140mph gauges do the same thing...It must be a wiring problem somewhere. Heres two vids of what I mean...

This one is where it just stopped working...
View attachment 154061

And this one is where its kinda jumpy and wants to work...
View attachment 154062

jrichker · Mar 6, 2012

Look closely at the wiring coming off the TFI module. One of the wires is dark green/yellow and is labeled IDM. It has a 22k K ohm resistor and the wire connects to pin 4 on the computer. The same wire feeds signal to the tach. If the wire is loose, damaged or the resistor is damaged, you could have tach problems.

Diagram courtesy of Tmoss & Stang&2birds

KaLiKo Street · Mar 6, 2012

I believe everything you just posted was for a 5.0 and that top diagram says for 88-91...mines a 92 with the dual coil pack 8 spark plug 2.3 for now...

Foxbody Tachometer "Jumpy"

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Foxbody Tachometer "Jumpy"

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