WMC1;
The few times I've seen this issue have been wiring related. Your last message is leading you in the most likely of causes. In addition to frayed or broken wires to the 6 pin throttle motor, also look at the ground connection under the left side step plate cover for possible connection problems. If you would like to have the bench test procedures for the throttle motor/sensor circuits we may be able to help you further. Do you have a clean fuel filter in the throttle body and has the accelerator pedal and throttle actuator been taught to the ECM.