clio 172 over revving,and going into limp mode

Driving along fine then all of a sudden car started to idle at 3000rpm,then it stops over revving and goes into limp mode it keeps switching between limp mode and just over revving, this morning whilst driving to work I was doing 60mph in limp mode,(flat out) then Speedo all of a sudden shot up to 90mph for a couple of seconds then back to 60,any ideas on what this could be before I have to take to garage,thanks in advance