hi,i have a 1999 dodge van 1500 with 3.9L .when i t is idling for 10 mins,it will start missing and it wouldnot reb up , it will be backfiring,stumbling, then all the sudden it will be okey.code says no 1 o2 sensor shorted to volts.changed sensor,checked all the wires ,also changed ig.coil,pick up coil,spark plug wires but same thing,i dont know but else to change except e.c.m. please help me. thanks