engine idles at 2000 rpm when hot, coolant comes out of overflow, no codes on 2001 Cadillac Catera

when more load is applied to engine the idle returns to normal but gradually increases to 2000 rpm. checked for exhaust gases in coolant, negative

Asked by for the 2001 Cadillac Catera
suspect vac leak 1st then poss t/body sticking
1 more answer
have you tryed the throttle positioning sencer