The tach on my RS was reading way high (1500 idle, about 4,000@70mph in 5th gear). So I got another gauge cluster out of another V8 RS and swapped the tach into my existing cluster. Well, it doesn't seem to have cured the problem...tach seems to be doing the same thing!!! The tach was working fine when pulled so I'm thinking something must be wrong somewhere in the wiring. Does anyone know how to find the tach wire on a 90-92 TBI car???

 

You might check over on the electronics board, they should be more help. I my self would like to know if the stock tach can be recalibrated.

Steve

 

what you really need is to do some datalogging, then you can see what RPM the ECU is actualy seeing. with the nature of the tachs in these cars, it would not suprise me one bit, if you new tach was also fubar.

 

It will be the white wire coming out of the grey connector on the ignition coil. There will be a test connector on it that you can disconnect and put a tach analyzer on it to find out what the actual RPM reading is from the coil.

 

Is this what you're talking about????

 

yes, that is the test port.