sometimes the tach in my coupe swings higher almost like it has very little resistance, then it eventually ends up going back to normal.



I have another tach in the car but its a little annoying seeing the factory tach swing over and the over-rev buzzer coming on.



any ideas?

my guess would be bad ground on the secondary coil. my tach bounced a little till i cleaned underneath the coil pack

I dont have stock coils, its a swapped engine, I will check the ground by the coil though

yeah how its is done? first thing to look at is the wire. step 2 depends on the setup

the second tach I have in the car is hooked directly up to the computer which is a true filtered signal, im pretty sure the factory tach is tied in the footwell by the computer but not into the computer itself, more into the wiring.

yeah on the lsx engine its from the ecu direct

i first had the aftermarket tach hooked up to the coil- not a good place for it as it dropped off at higher RPM, put it to the computer and its a nice accurate signal

yea oddly the lsx engines output a 4 cylinder tach signal from the ecu... and it just so happens the volvo tachs are also all 4 cylinder, even though some of them are 5 and 6 cylinders

acting "screwy" is usually a connection issue