1G 1990 DSM tach jumping.

[blazekid71]

1990 GSX. Cleaned all grounds. Added 2 ground straps. Changed coil pack, changed gauge cluster and bypassed noise filter as in above reference. Tachometer works fine until engine is under a load after 4000rpm then Tach starts jumping around then drops out. Any help would be appreciated. If I need to order a new tach filter and take out jumper on filter harness I will do so. Thanks Scott

 

[danl]

A jumping tachometer would be exactly what I would expect if the noise filter was not functioning or bypassed.

 

[steve]

1990 GSX. Tachometer works fine until engine is under a load after 4000rpm then Tach starts jumping around then drops out.

What year is your ECU? Original?