The tach I just installed seems to jump to 750ish rpm before I turn the key to start the car (in other words go past all the clicks, but don't start yet). Then when I do start the car it appears to have a high idle (around 1600-2100 depending on how warm the car is), but then when i make the car go it shudders around 1000 rpms and then dies around 750.

Is this an issue with tach itself or calibration issues? If it is a calibration issue then how do I calibrate it? Any help or insight is greatly appreciated. Thanks!

 

I would like to also add that my previous tach had an issue, but it was very different. It would float around and bounce up and down 500 +/- or more rpms and would sometimes just drop to 0 or shoot up to 9k+ rpm while driving casually or at an autocross. I guess I'm wondering if this is possibly a cluster issue or wiring issue too. Any feedback would be appreciated and thanks in advance.

 

Can someone at least confirm that if it's abnormal for the tach to jump up to 750 with the key fully turned, but before starting the car? I believe this to be abnormal and my previous tach never jumped up to 750 in this position, but since I believe my other tach is faulty (or possibly even my cluster) I am not sure how it's supposed to operate. On the bright side this tach does not seem to jump around like my last one and at least gives me some ballpark idea where I'm at.

 

Hey,

I had to replace my old tach for another one due to the same symptoms like erratic idle.
Now with this one it loves to just sit at 2000rpm even when the cars off. So it adds 2000rpm to what ever rpm I am at. ex: 2000rpm on the tach = 0rpm, and 6000rpm on the tach = 4000rpm.

Im going to pull it apart just just push the needle down. see what happens.

 

if you need to replace the tach, Im upgrading my gauges and I have a perfectly functional '94 tach that Ill be pulling out of the cluster in at the end of the week.

 

Let me know how this goes FD3S-K? I haven't had a chance to take the cluster out again to reinspect, but and try cleaning to fix the problem. Your issues sound similar to mine except mine was adding in about 750-900 rpm extra because it would rest there after I turn the key over, but not start the car. I've just been dealing with it and just shifting when I hear the beep sound come on (according to my tach it's coming in somewhere around the 9kish range)

Monsterbox PM me how much you would be willing to sell that tach for because I might be interested.