Re: 97' Windstar downshifts with no reason
Replace the IAC (idle air control valve) and TPS (throttle position sensors). Both are located on the throttle body/intake. Cost about $40ea - shop around! Dealers charge twice that, easy. You CAN clean the IAC, but if you move the plunger in the sensor more than 1/4", you'll have to replace it.
A bad TPS leads many shops to misdiagnose the problem and claim it transmission related, but it's not. A faulty TPS can lock/unlock the torque converter at speed. You'll more than likely notice that if you use cruise control, the problem will be more pronounced. It's good measure to replace the IAC as well, as they normally fail close to one another.
'00 Durango R/T 360ci 290hp (modded); 138,500m
'06 Pontiac G6 GT 3.5L 220hp; 44,000m
'12 Chrysler 200 Limited 3.6L 283hp; 13,000m
'99 Taurus 3.0L 2V Vulcan 145hp; 154,300m - Traded
Amsoil in all vehicles!