spedo goes crazy and gas peddle cuts off and on:help me plz

k my gas peddle when im driving will just not go like there is no rpms when all the way floored,then cut back in on its own then just keep repeating its self with that,while doing that the spedo will jump from 20mph to 120mph,and the gas will work when the needle starts going back to the speed its supoz to show,which by the way its telling me how fast im going so yea and the car jerks through all of this.i changed the spark plugs today and it seemed to help but it still does it,its a 99 gt.help me please this is freakin annoying.no its not the rev limiter,this affects the car in regular driving,il be going like normal down the street and the gas will cut out and the spedo will just not work because it is going crazy it is sumthing big i can tell.

Welcome to AF.

I think you are describing the rev limiter,
its supposed to keep you from over reving the engine.

Sometimes in Park when I rev my SE the speedo jumps up a little :dunno:
Just Another Grand AM gremlin I suppose :grinyes:

I believe that "99"s describing a lack of response when he presses the accelerator, like maybe the TPS is off line.