I have a 2001 petrol 100 sx, I am a new driver so dont know much about cars, so was wondering if anyone can help, even my garage dont know whats wrong and I cant afford their "trial and error" approach.

When I am sitting idle at traffic lights etc. with my foot on the brake, the pedal will pull down a little on its own. Immediatly after this the revs go from standing at 10, to jumping up and down between 5-15 by itself, after about 5 seconds of this, it cuts out completely with all the warning lights as if I had stalled it (yes i've stalled her a few times lol). Shes just had her timing belt replaced, but no other work that I know of.

If anyone could help it would be greatly appreciated as I love my little car but cant afford to mess about with rolling cost trying to find the fault or a big repair if ignoring it makes it worse.

it is i think the throttle sensor ,i had the same problem i put some contact cleaner in the connecter and problem is gone.the connecter is located under dash on passanger side,it is a white connecter,the wire comes from the pedal,good luck

Thanks, cant figure out how to do it myself but at least i have something to tell the garage, much appreciated