tachometer works only half the time???

[91orangeGST]

I just bougt a 90 turbo laser and sometimes the tach doesnt work. What happens is in second and third gear when it goes past 4 grand it will just drop until I let off the gas. So I thought maybe a wire is popping on and off, so I wet up in rpms real slow and it still did it. My acceleration is fine, so I dont know what it can be? Could my ECU be going out? Also des any one know what the speeds are for red line in each gear for a 90 turo laser?

1/__mph 2/__mph......

Kyle

 

[steve]

Check which ECU is actually in the '90. It's possible someone put a '91+ ECU in.

Steve