Try playing with the wires under the front seats. I have fixed that same problem on a Caddy, a Chrysler, and a Ford this way.
Lots of luck.
89 LX Notch: Floo-Tek 5.0X heads, GT-40 intake, B-303 cam, Dynamic 3800 converter, 4.10:1 gears & lots of suspension work. 12.50 @ 106.42 MPH.