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post #1 of 4 (permalink) Old 03-29-11, 12:37 PM Thread Starter
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97' Windstar downshifts with no reason

I am having a problem with 97 windstar 3.0 GL. It has started to downshift at steady highway speeds randomly. What happens is that on steady spees(no cruise) I feel a engine braking and RPM goes about 1000 rpm higher and after few seconds it upshifts again. What could cause this? Transmission works fine otherwise firm shifts and no slipping. Fluid level is ok. TRS and VSS were replaced a year ago(Standard). There are no trouble codes in PCM.


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post #2 of 4 (permalink) Old 03-29-11, 05:03 PM
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Re: 97' Windstar downshifts with no reason

Maybe the wire in the shift lever is damaged and causing it to go in and out of overdrive. Try the button and see if it fels the same. Pull the covers off of the column and check the wire.

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post #3 of 4 (permalink) Old 04-03-11, 04:32 PM
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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.

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post #4 of 4 (permalink) Old 04-03-11, 04:34 PM
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Re: 97' Windstar downshifts with no reason

I'll also mention that a bad TPS/IAC won't always generate an engine code until the sensor is nearly toast and you're stuck on the side of the road. Occasionally my older Dodge would light the sensor up on longer drives, but the code doesn't pertain to a bad sensor, I think the last one was something similar to a misfire or something totally unrelated.

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