braking for a stop sign, engine suddenly for no reason increased to 3500rpm.
very scary so shut engine off. restarted ok.
anyone have this prob?

Welcome to AF, foot on brake, engine hit 3500?

yes. in drive. local mechanic thinks transmission as nothing shows on dash. eg:no engine check light

The idle air control has no capability to force the engine to 3500, something else is going on here.