Overdrive and Torque converter lockup

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Vehicle in question: 2003 Ford Taurus, 4 spd auto, driving on level ground.
When I accelerate form rest, I can watch the tachometer and follow what gear my car is in. I can feel/hear/see it shift from first to second, second to third, and third to forth. Some times when it shifts into fourth, usually under moderate acceleration, it does almost like a double shift, I assume this is torque converter lockup. At this point, cruising at about 40 mph(1600 RPM), if I push the gas peddle a little harder, the vehicle will accelerate, and the RPM will slowly increase, and if i gently lift off the gas, but not completely, it will decelerate, but the torque converter will remain locked down to about 35-38 mph (1450 RPM). I am pretty sure this is the expected operation of torque converter lockup.
However. If I am cruising at about 35, and very gradually creep up to 40-42 MPH, it will not go into torque converter lockup. The engine will hang around 1900 RPM. Then, If I gently push the gas a little harder, as if i wanted to accelerate to 50 MPH (but stayed at 45) the torque converter will immediately lock and the RPM will drop to 1600. At this point I can lift back off the gas slightly, back to where it was before I gave it that little push, and it will remain locked, but as soon as I lift all the way off, it will unlock, and it will need another little push to get it to lock again. The question is: Is this normal, and if it is, why? I would think it would be the other way around, and lock faster under less acceleration. If this isn't normal, is there a way to adjust it.
The reason I notice this is because every day I drive a certain road, about 1.5 miles long, speed limit 40 MPH. this road has curves, so when I go around a curve, I lift off the gas, and the torque converter unlocks, but as soon as I put my foot back on the gas, even though it never really decelerated any, it will keep cruising at 2000 RPM, and not lock up again. The potholes also make it hard to keep your foot steady on the gas. If there is no one in front of me, i can keep it locked up the whole length of the road, but as soon as I have to lift off the gas, it will unlock, and stay unlocked for the rest of the length of the road.

Wow, that was long:ohcrap:

posted by  dvdrose18

come on, somebody must have some idea, And VW ain't been around to give you grief if you're wrong:laughing:

posted by  dvdrose18

When reading through the description, I think you ate trying to understand how your automatic tranny operates under your specific driving conditions.

Tour tranny could be doing a couple of things. You are @ the point where your torque converter is locking-up/unlocking and you not downshifting from 4-3

On roads like the one you are describing, drive the car in 3rd and see if your drivability improves.

Are you getting codes from your ECM

posted by  tbaxleyjr

Drivability isn't really an issue, as far as i know it is working the way it should, and it has probably acted like this its whole life, I just noticed it recently, now that i pay more attention to what my car is doing for fuel economy's sake.
Let me try to understand a few things here.
1. Is the torque converter supposed to unlock when you take your foot off the gas, or not until you press the brake?
2. Is the torque converter not supposed to lock until the vehicle is at normal operating temperature?
3. is the torque converter supposed to lock in any gear besides 4?
I believe the torque converter in unlocking like it is supposed to, unless you have a different answer for #1 above. My question is, why won't it lock back up again.

almost unrelated, but your suggestion to downshift reminded me. In my car, for as long as i have had it, If I manually downshift, at any speed, into any gear, my car will accelerate for about 2-3 seconds. By accelerate i mean that it will actually pull down the accelerator peddle, much the same as cruise control will do, the RPM will jump up, and the vehicle will accelerate forward. This even happens if i move the gear selector to a gear that it is already in. I could be rolling at 10 MPH and move the selector from Overdrive to drive, and it will accelerate for 3 seconds, to about 15 MPH, and let back off again.

I will try shifting into 3rd on my way home tonight. I would try it now, on my way to school, but it almost never locks up, I believe because the car is still cold.

posted by  dvdrose18

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