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SUVs Toyota Highlander Toyota Highlander Transmission Problems
230 messages, Last post on Dec 01, 2009 at 9:52 AM
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Replying to: wwest (Oct 13, 2009 9:20 am)
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Replying to: minnesnowta1 (Oct 14, 2009 6:02 am) But there are 1 or 2 functions that require "linear" displacement of the solenoid actuator plunger, line pressure control for instance. Eons ago it was considered that a simple electric solenoid could not be used in this manner. Then along came the idea, ability, to modulate the plunger position "linearly" via the use of PWM, Pulse Width Modulation, voltage duty cycle control of how far the actuator was to be deployed. The next problem was, what was to be used as feedback to the controlling device to denote the actuators control position...?? A new off-the-shelf solenoid could be roughly "calibrated" insofar as voltage applied vs actuator movement/position and while that might be close enough for the factory default control mapping parameters it was not satisfactory for the fine position tuning control required once installed within the vehicle. The answer was...The function being controlled. Clutch slip within the transaxle...?? Increase the line pressure via a slight increase in PWM voltage. You didn't need to calibrate the solenoid to exacting actuator position, that could be done "on-the-fly" as the vehicle is driven. I believe the first use of this technique for automobile engine control was to control the idle air bypass valve. Two feedback sensors are used to do this, the upstream oxygen sensor an an engine RPM, timing sensor. The solenoid must be adjusted to the point of allowing just the right amount of air through the bypass port that the idle air/fuel mixture is correct in accordance with the upstream oxygen sensor(s) and the RPM remains at a steady 800RPM. Disconnect the battery and the IAV control will default to the factory parametric PWM settings, but after a fairly brief period of time the ECU will have learned, pretty much exactly, what level of voltage is required to hold the solenoid in the correct "linear" position to satisfy the feedback parameters. Now it will go to that "setting" each and every time you start the engine. Plug up the bypass port slightly with debris, oil wicked into the intake path from a K&N followed by dirt, the ECU will simply re-learn, again and again, over an over again, the level of PWM voltage to be used to "meter" the proper airflow. Plug up the bypass port too much and the solenoid will not have enough range, you get a CEL. Clean the bypass port and over a period of time the ECU will have learned the new parameters. Disconnect the battery and that period of time will shorten. |
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Replying to: minnesnowta1 (Oct 14, 2009 6:02 am) What your service manager doesn't understand, "get", is that there are two categories of ECU learning/relearning. Yes, the engine/transaxle ECU will "watch" how fast you "normally" depress the gas pedal AND how fast you "normally" release it. The time it takes you to move your foot from the gas pedal to the brake is even important insofar as adapting to a specific driver's driving style. But parameters of/in that category MUST be erased for each an every stop/start engine cycle. But there are MANY other engine/transaxle control parameters that must be learned and/or continually relearned as you drive. Let's say the knock/ping sensor "sounds off" during acceleration (excluding engine lugging with a stick shift and/or ignition timing too early). The ECU must quickly adjust, enrich, the A/F mixture via EFI to abate the knock/ping. But now the engine will be operating below the factory design "standard" and the ECU will periodically run A/F mixture leaning, optimization trials, in case the engine is now being "fed" with the proper, premium, fuel. |
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Replying to: fixrixsix (Oct 13, 2009 7:18 am) Thanks
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Replying to: minnesnowta1 (Oct 15, 2009 7:00 am) Again, just to be clear, I had my engine replaced and the car immediately starting bucking/jerking in the lower gears (like, within 5 miles of leaving the service center). This is appearing to be an issue related to the computer/electronics as a result of how the replacement engine is "talking" to the car/transmission. Curious thing is that one would think that Toyota or the shop that replaced the engine would have experienced this before. That is: Engine replaced = car doesn't shift properly. But they are stumped. They still have my car and are now talking to some other "expert." It has become a bit of a lab experiment, I think. I will tell you this...I have owned 10 cars in my lifetime and will NEVER buy another Toyota. If I had taken the time to read all the negative things on the Internet about how poor their customer service is, I wouldn't have bought the Highlander either. I think Consumer Reports must be getting bought off by Toyota.
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Replying to: fixrixsix (Oct 15, 2009 8:50 am) That may mean, in effect, "jumping from the frying pan into the fire." Is there, today, a "better" marque overall...?? |
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Replying to: paul143 (Sep 22, 2009 4:13 pm) Back to the dealer I guess. Have you had any luck getting yours fixed????
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Replying to: minnesnowta1 (Oct 21, 2009 5:49 am) |
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My owners manual does not cover the auto transmission for some reason. It states the type of trans. fluid to use but does not state the correct way to check the fluid level. Can someone help me? Is there a "supplement" manual out there that someone has heard of ? Thanx...............................
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