Cold Weather and CVT

Thanks for the feedback. It is not drastic enough to make a special trip in to the dealer, But I am definitely attuned to it, and will watch it to see if it gets better or worse over time.

I hope it is just a part of the system breaking and and will become unnoticable over time. If it is an issue that needs to be addressed I will certainly post my experience here.

 

Gosh, you described EXACTLY what we just experienced driving at 1 degree F. This is not normal. Our 2002 never did this. I was sorely tempted to pull over as well. The car would willingly accelerate to 70 with NO foot on any pedal. I didn't touch the accelerator the entire way home, just rode the brakes thinking I should stop and get a tow and if it had been more than a mile and a half, I would have. Oddly it surged backward as well, making me think it is the CVT and not some strange engine problem. More to the point this not the car trying to keep its charge, it didn't charge at all the whole way, I expect because the excess torque was too much for the generator. There was a LOT of excess torque. Arrived home to the stench of sulfur (presumable from the catalytic converter) and the hint of overheated something else.

This reminds me that the other day, probably the last time it was driven, I pulled out fast from the post office, the wheels were slipping on the wet pavement and the traction control was kicking in and it responded very oddly, like the engine was braking loose because it couldn't turn the wheels with the ABS locking them down. Hm. That would be a bad design if that could damage anything, but I remember thinking at the time that it felt like a "bad moment".

It is going in first thing tomorrow, while it is still cold enough to replicate the problem.

 

Runaway acceleration should get the attention of the dealer. Especially if you use words like "liability" and "lawsuit."

I wonder if the HSD is failing to coordinate engine and motors to control revs, or maybe it's the drive-by-wire accelerator pedal.

I would have guessed both of those would trigger a DTC code, though. Have them scan and SHOW YOU THE SCAN.

 

I've noticed that too on the highway. I assume that is has to do with the control system constantly trying optimize the performance. If you're at condition that is a transitional point between two settings, it's likely that the car will alternate back and forth between them. When I turn on the Energy Monitor, I'm always amazed how quickly the energy flow changes.

On some of the vehicles from the twentieth century, there was an overdrive override switch. The main purpose was to disable the last gear (overdrive) when the car was in a condition where it was constantly switching back and forth between the two gears. In the case of an automatic transmision, it probably wasn't too good for the system to be constantly switching gears. However, in the Toyota HSD system, it has been specifically designed to constantly reallocate power flow between the ICE, MG1, and MG2. While there is no adverse effect, it is perceived by the driver the same as the driver with an automatic transmission when it is hunting for the proper gear. That said, if I paid close attention, I probably could sense the "surging" again, but now that I've gotten used to it, I don't really notice it anymore.

Also, it's not possible for the CVT to actually slip since the Toyota system does not use belts, only gears and chains. There can however be a perception of slippage since the control system can speed up or slow down the engine independently of the vehicle's speed. When the engine slows down, we just think the car is running smoother, but when the engine speeds up, we incorrectly perceive it as slippage.