. The RPM gauge is acting funny on the dash = zero rpm"
the wiring does not seem right to the tachometer.
the tach does not wire to the 3speed PRNDL switch on right side of box ,
the PRNDL does tell the ECu that more aggressive idle controls are needed for in R or D OR L.
The tacho, simple reports the spark rate (converted to RPM) Tacho is pure SPARK RATE (frequency) the spark hit rate is scaled to RPM.
i made this long ago. on 91, see the cruise here, find that box and unplug it, if present it could cause vary bad things, that I will never understand. (never had one)
the tachmoter is like 1 meter, 2 transistors., 4 caps and that is it , it has integrator that converts pulses to needle volts that is right the meter is voltmeter for the tacho.
![[Image: tacho.jpg]](https://www.fixkick.com/ECU/tacho/tacho.jpg)
the wiring does not seem right to the tachometer.
the tach does not wire to the 3speed PRNDL switch on right side of box ,
the PRNDL does tell the ECu that more aggressive idle controls are needed for in R or D OR L.
The tacho, simple reports the spark rate (converted to RPM) Tacho is pure SPARK RATE (frequency) the spark hit rate is scaled to RPM.
i made this long ago. on 91, see the cruise here, find that box and unplug it, if present it could cause vary bad things, that I will never understand. (never had one)
the tachmoter is like 1 meter, 2 transistors., 4 caps and that is it , it has integrator that converts pulses to needle volts that is right the meter is voltmeter for the tacho.
http://www.fixkick.com