VERY WERID - engine revs by itself???

when the car idles, sometimes the rev counter goes up to 1500 and then dips below 500, as if someone was reving it. this happens sometimes and doesnt happen others. but it seems to be happening more and more now over the last 2 days. then this morning started it and floored it and it starting choking, spluttering...

does nayone have any idea what this could be or if its happened to anyone b4, how did they fix it.

thanks a mil in advance if any one can help.

I am having a similar problem with a 1994 R19 1.4 energy with a Bosch carburettor. The idle Step Controller underneath the throttle crank, which is controlled by the car's computer is opening the throttle slightly when it shouldn't. You can actually watch this happening if you stand on the right hand side of the car with the engine running and the air filter removed. Since the Controller and the computer are clearly functioning the fault must lie with the data (engine speed? Vacuum? Temperature? Question mark?) that is being fed to the computer. It is the origin of this data that I would like to know about. Isn't it typical that this model of carburettor isn't in the Haynes manual which is supposed to cover this car :-(. As a temporary measure, I have unplugged the idle Controller while it was fully retracted but this has made the car a bit lumpy when cold. I know this thread is rather old and its originator has probably solved his problem or got rid of the car by now! But if anyone has anything to offer on the subject I would be most interested.