It sounds like the throttle positioner sensor is bad. The engine most likely reves in the AM and that is the vibration and hum. Also, a bad TPS will cause a fluxuation it the engine speed.
Let me know if this helps. Also, you may want to have the computer scanned for codes. Most nationally recognized psrts stores will do it for free, and it may identify the exact problem.
Friday, November 21st, 2008 AT 8:44 PM