eratic idle

i have a 93 ford ranger with the 3l. engine. besides being really poor in the gas mileage dept. it has lately started with the idle surging up and down , from an almost stall situation to about 1500rpm. i have not found any codes and was hoping that someone else had had tyhe same problem and could enlighten me sam

Try checking your idle control valve,mine used to do that except it would only rev real high.It is small round part near were the the throttle cable is attached to the butteryfly plate.Only two bolts hold it on and.