Had this problem with my 1.6, turned out to be the throttle cable was sticking so I just got it replaced.
However, could also be the carb, if it really revs high when you first turn the key in the ignition, then settles down, then that's definitely the problem.
I have a crap carburettor in mine, it either revs really high or just drops so low it stalls, it's a right pain in a$$...get a Weber! They are far more reliable and your car will be quicker too
