1G ECU swap?

[mitsubishimanic]

so im switching my ecu from a 90 noneprom to a 91 eprom i have an after market tach i want to install. so do i still need to change the wiring to make the aftermrket tach work or can i just in stall the ecu then wire the new tach in

 

[steve]

The aftermarket tach is unlikely to care about the difference between the 90 and 91 ECUs but it needs a good signal and it's not clear that you actually have a good tach signal right now.

You can also get on of the boards that convert the signals. I usually put them in the ECU converting the 91+ ECU to act like a 90 ECU as far as the tach signal. KeyDiver sold them and I still have a few. That allows the factory tach to work with the converted 91+ ECU.

This is only an issue if you have a 90 car and try putting a later ECU in it.