My tachometer reads about 3k rpm at start up (just idling) and when warm, it's around 2k. I wasn't sure if the tach filter was the issue because I read it makes it jumpy but mine appears smooth so to say. There doesn't appear to be any leaks but I wouldn't even think it could reach 3k with a vacuum leak (Also there are no codes). Do you think I may have a tachometer issue? I read this page [url=http://www.howtoalmanac.com/kevin/projects/automotive/tachfix.htm][/url] and he said you could solder a potentiometer on then calibrate it using a frequency generator + oscilloscope. I know people w/ the equipment but I was confused on whether this is the fix I actually need; to calibrating it with the engine like he mentioned. Any replies are greatly appreciated.

[This message has been edited by PribanicS (edited 02-13-2014).]

quote Originally posted by PribanicS: Do you think I may have a tachometer issue?

Probably, as it's not uncommon.

Have a look at This thread.

quote Originally posted by PribanicS: and he said you could solder a potentiometer on then calibrate it using a frequency generator + oscilloscope. I know people w/ the equipment but I was confused on whether this is the fix I actually need; to calibrating it with the engine like he mentioned. Any replies are greatly appreciated.

I do this routinely for the firebird cluster swap into Fieros although the same fix can be applied to the Fiero tach. I have a V8 cluster in my V6 and a V6 cluster in my V8. The only way to get a tach to play nice in those circumstances is to change the resistor. Some folks mess with the capacitor and I tried that and it's waaaay more difficult. With a variable resistor and frequency generator it's child's play to dial it in to the correct value.

I don't have an oscilloscope but I do have digital wireless tach. Is there room with the car tach plugged in to adjust the potentiometer to the correct resistance?

I did the above fix and worked great for me. Tach is still a LITTLE off the higher you get (at 3500 on tach is about 3300 on diagnostic cable).

Before fix I swapped two different tachometers. Both had similar symptoms . Would read about 1200 idle.. and would QUICKLY climb, where 5000 was just about 2000 in real rpms.