I was driving on the highway today in 5th gear with the cruise set at 70 and my tach bounced from 2k to 4k so i mmediatly hit the brakes and turned cruise off and my tach kept bouncing around from 2k to 4 or 5k i pulled over and stoped and it went back to normal...it was obvious that my engine was not reving that high so im thinking it is a sensor or something. any suggestions?