i have an 01 4.6l screw and when i dont plug in the block heater and the motor gets down to less than 30 degrees when i start it up in the mornin it wont switch into closed loop mode, and the check engine light comes on with the codes p1132, and p1152 saying "lack of ho2s11 and ho2s21 switching sensor indicates rich" but if i plug it in all night, or an hour or two before i start it the sensors switch just fine. anyone got any ideas what would be causing this?