2003 Chevy Venture LS Van-Occassionally, van accelerates without using cruise(even if disconnected) or gas petal. Seems to happen at different speeds, but tops out at 40-60mph and maintains speed unless going UP inclines,then slows. Tapping brakes does not stop unwanted acceleration/speed,but will stop car if brakes applied firmly(thankfully). Mechanic cleaned throttle body on 2 separate visits,on 3rd visit ran complete computer system scan-Hads(?) codes no codes,checked idle counts good,checked TPS count good,checked coolant temp & ECT good,found archive on identafix which referred to C305 connector which was full of water,cleaned terminals & repacked with dielectric grease,cleaned battery cables. Test drove and declared fixed. Started acting up again within 24hr. Same occassional unwanted acceleration as before.
HELP- running out of patience and $$$
Maybe there is a mouse or chipmunk residing in your air intake and every time it it tries to escape through the throttle body, it jams the plate…Just a thought…
Perhaps the ECM is varying the timing, which will also vary engine speed without any throttle input…