My 1994 Bonneville accelerates even when I am not pressing the gas pedal. This begins as soon as I start the car. When put in neutral or park, the RPMs kick up to and remain around 3,000. On the road at high speed, conversely, (~60mph), the RPMs occasionally remain worryingly low (around 1.5-2 thousand) even when the gas is used. When I brake I feel I am fighting the car. All the gauges read normal (although the car warms up quickly if left in park at 3,000 RPM) and I'm getting no check engine light. What could be causing this?