Car trouble with a 2000 ford mustang v6.?

[Sam]

I have 2000 ford mustang V6 with automatic transmission. Sometimes when I try to pass another vehicle at about 55 to 60 mph and i step on the gas the rpm goes up to 4000 but then it feels like the engine begins to quiver and it wont go past 4000 rpm no matter how hard i step on the gas. This doesn't happen all the time. Any ideas as to what the problem might be. Thank You

 

[Kev]

sound to me that it is the veh. Rev limiter that prevents over reving the engine