1992 Toyota Previa 4 cyl Two Wheel Drive Automatic
Recently my Previa has been shifting in and out of overdrive. Sometimes only sporadically, more often it is beginning to shift in and out every 1 or 2 seconds. When I push the overdrive button to turn it off, it runs ok, but I can still feel a sort of 'chugging', but not anything like the shifting in and out when in overdrive, which becomes a head banging, neck jerking experience. I took it in for service to a transmission specialist. No codes appeared faulty on the diagnostics, so on a 'hunch' they replaced the throttle control valve. This did not fix the problem. They told me it may be an electrical/electronic issue that they were not capable of assessing, possibly requiring a new computer. Any suggestions?