I have a 91 spirit rt. My speedometer and sometime the RPM gauge is acting very strange. After it has set overnight it works fine until I have turned the car on for approx 5 minutes or so. Then it starts to shake erratically for a minute or so and then seems to settle about 10-12mph too slow when I am really going 60mph. Every now and then when I am riding it pretty hard, the rpm guage will fluctuate wildly for a short time.
Does anyone have an idea? Is it a sensor problem or wiring harness problem? Thanks for input.