it only idles hard in drive. when i open my hood i see this little shock absorber looking thing by the belts , and its loose and vibrating. a buick/gm tech couldnt figure why my a/c compressor wasnt engaging. hi/low pressure switches are ok. i have read that it could be a loose belt. havent checked that yet.the engine has a vibration thats hard to feel in park or neutral,but its bad in drive at idle and is felt through the steer9ng wheel.and i wondered if it could be this shock thingie. what i want to know if this could cause my a/c/ belt to loosen and could it make the engine vibrate