06 grand prix flutter in high speeds

[jdmn]

06 grand prix with 218000, @ 60 the car doesnt flutter, but at 70 it starts jumping, tranny fluid temp hits 208, once in a while it shifts hard between stop signs. Don't know bout maintence on it just got it. Speed sensor? Converter? !also it smells like its running rich, catilliac converter? Fluids are good. Any ideas?

 

[JulesMaximus]

06 grand prix with 218000, @ 60 the car doesnt flutter, but at 70 it starts jumping, tranny fluid temp hits 208, once in a while it shifts hard between stop signs. Don't know bout maintence on it just got it. Speed sensor? Converter? !also it smells like its running rich, catilliac converter? Fluids are good. Any ideas?