Factory tach has a mind of it's own

[sirr0bin]

Hey guys, I just pulled my car out of storage and now the tach is messed =(

It basically just sits dead around 600rpm, if I go over approx 2500rpm it suddenly shoots up to about 4000 and then dies back down, and if I step on it the tach just spins past 7000!

Every now and then it kicks back in and works normally, but not for more then a minute or so.

Any suggestions on what I should look for? Chiltons manual was no help, and I'm not sure what module/cable would control the tach

 

[Mike92GT]

Most likely cause is that the Tach itself is bad. Mine started acting up a while back, I replaced it and problem solved

 

[mustangjoe87]

I have heard of a TFI module causing irregular tach function