Okay i recently picked up a 91 240sx & im having a problem getting it running correctly.

Symptoms :
Gauge cluster either sits @ 0 mph or jumps around like a wild child.
Car runs fine till it reaches full operating temp then once it hits 1800-2300rpm's it starts to hesitate/jerks then will clear up.Also Cars CEL pops on when it starts to hesitate/fall on its face.
Car idles poorly.

What iv done:
Changed the plugs
Checked the timing
Gone over the few grounds that i see.
Fresh gas/seafoam


I found a bad engine ground that was nearly cut in half Replaced it the car ran fine for about 4 hours then started acting up again. Could there be another ground somewhere that is faulty or anyone have any other suggestions? Maybe a bad ground to the fuel pump?

Any response is highly appreciated
Thanks James