Tachometer Check

Attach an external high quality tachometer to the engine speed detection connector on the harness side (such as with a paper clip).
NOTE: For tachometer check, use an external high quality inductive tachometer.

Fig 1: Measuring Tachometer Using External Inductive Tachometer
Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
Compare the readings of the vehicle tachometer and the external tachometer at every engine sped, and check if the variations are within the standard values.
Standard values:

Fig 2: Identifying Standard Values
Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.