I have a 90 corvette coupe, 6 speed, Z51 and FX3 options, 93k miles. Had a plug wire that kept jumping off so I decided to replace the original wires with Granatelli stainless core wires from Mid America ($100). Also replaced the distributor cap and rotor. When I started her up, the whole digital readout, including the speedometer, gas gauge, odometer and gas mileage readout went into spasms. By spasms I mean that the numbers were scrolling, were cut in half, were changing from US to metric, you name it, and the changes were coming every1-2 seconds. I unhooked the ground from the battery, waited a few minutes, hooked the ground back up, started it and had the same thing, except now the select ride control dash light came on and the auto A/C light and fan light started blinking. This was last Saturday. On Sunday I drove it 21 miles to church, the select ride control dash light didn’t come on and for the last 2 miles of the trip, everything on the digital readout went back to normal. The outside temp at the AC control showed as 24 degrees (it was really 80) and the heater came on. Driving home, the digital readout was OK for 1/2 mile, then went crazy again with an occasional10 to 30 seconds periods of normalcy. The AC also straightened out. Does anyone have any advice, or has anyone had a similar problem. It had to be me that messed it up. I tried to route the wires the same as the originals. The only other thing besides the plug wires interfering could be when I replaced the distributor cap, in removing the coil from the original cap and putting it in the new one, I sort of stretched the coiled wire attached to the small contact that comes through the top of the cap and goes through the rubber seal. Thanks for any help you can give.

 

You have made a lot of changes. One thought would be to look for a bad ground or loose wire on either side of the fire wall. Or, you can start going back to square 1 and retrace your steps.

I don’t think the plug wires would do this. But a defective part, or poor installation of parts in the distributor might be the cause. Arking could exist. I would work my way back to original configuration and replace any broken parts in the distributor. Once you get the dash under control, you can move forward again.