Questioni have a 92 previa w/ 154k miles. its been a great vehicle but reciently began loosing power in cold weather and first thing in the am. the van is a little jerky between 0 and 5 mph and then again around 30 mph. at about 30 is where the tranny shifts to third gear. the frustrating thing is that it does not do it all the time. my local toyota dealer doesn't lead me to believe they know anything. i left it there for two days last week and they never did find a definate problem. i have had the tranny serviced and the rear axel serviced. i have not had a regularly scheduled tune up in 30k miles.
anything you can let me know is very appreciated.
AnswerHello Jerry, welcomr to my expert page.
Since you had it at the dealer for two days and they could not find anything I will assume that the obvious causes were checked.
The Previas had a problem with the throttle position sensor(TPS)wire harness, what happens is that the wires near the tps seperate inside the harness, since the transmission has to have this input signal to set shift points things can get a little screwy because it doesn't know whether to up or downshift, this is the jerky condition you mentioned.
We have known about this for years and I don't understand why your dealer doesn't know, I think there was a bulletin issued for this.
The fix for this is to replace a portion of the wire harness with a new connector for the tps, there is a part number for this sub harness but I will have to look it up, if your dealer can't help let me know and I will get the repair kit part number for you. Please remember I'm basing this answer on the assumption that all other possibilities have been eliminated.
