I have 1997 Buick LeSabre V-6, but like a week or so ago I started hearing this loud clunk noise when I'm parked, it just sounds like someone jumped on my trunk. When I back out sometimes and put it back in drive it makes a loud sound. Also when I push the gas pedal it putts like when your out of gas but I know I'm not. It also shakes when I'm on the highway, and when I turn a curve it's like my tires have no traction what so ever. And my gas gauge broke.
Have the LeSabre's front and rear suspension checked for loose or worn suspension components for your clunking noise. Check the tires for uneven wear, balance and alignment. There is a technical service bulletin (TSB) that might apply. It is called "Info on popping or thunk noise from left rear of vehicle.
Sierra, regarding the other issues, does your check engine light come on when the vehicle feels like it has no power? Scan your vehicle's powertrain control module to see if there are codes stored which are ignition-related or fuel-related. Check your fuel filter and the fuel pressure, are the spark plugs and ignition wires okay? You can find the procedures, specification and technical service bulletins (TSBs) in your ChiltonDIY subscription.
There are several fuel-related TSBs for the 1997 Buick LeSabre, including a newsletter for a fuel gauge that is not operating that may apply. Check the TSBs and Recalls section in your ChiltonDIY subscription. Use the "System" filter and select "Air and Fuel Delivery" to speed your search as there are hundreds of bulletins that apply to the 1997 Buick LeSabre.