wbrusseau

This is the first hybrid I have owned. I bought this vehicle used in July. I've noticed when the electric engine first starts it sometimes jolts the vehicle. It feels like the vehicle would be jolted forward if it wasn't in gear and if the parking brake was off. Anyone else experience this? Is this normal?

salimshah

"first start" needs a bit more explaining. Do you mean the very first time the ICE works you feel the jerk, but on later starts [with engine warm] the starts and shut down are seamless?

Salim

ukrkoz

There should be no "forward jolt" in P. As no drive PSD combination is engaged. This should be felt as slight shudder. Sometimes it's less sometimes more perceptible. But just a shudder.
Now, when you sit at say red light, with D engaged, brake pedal pressed to prevent forward progression, and ICE kicks in - sure, there will be a minor forward jolt. Minor is key word.
Never forget - you do not have a normal transmission, no clutches, not even CVT. Yes, I do know what Toyota calls it. They had no better name to register that for federal regulations purpose, so they called PSD a CVT. It is not. It is planetary gear set coupled with motor generator. Animal on its own.

salimshah

Not trying to be an alarmist, but just sharing information.
There is a clutch that exists in the bell housing, that mechanically connects the engine pressure plate too the transmission. It is very much like the foot pedal operated clutch but always engaged with the sole purpose of allowing slip when the rims of the engine and the transmission input do not match. Matching engine rpm to the MG1 is one other consideration at different times.

Back to my suggestion to OP, narrow down when it happens and discuss it with the repair facility.

Bottom line is . the observation is not typical. There is little the owner can do [other than frame the problem for easier identification].

ps: Based on information gleaned off Toyota prius/highlander ecvt explanation

Salim

salimshah

NateJG:
The clutch is between the Internal combustion engine and the MG1.

Salim

ukrkoz

There is no clutch in PSD. There is a device, rightfully named as torque absorber, that LOOKS like clutch but it is not. it is torque dampener plate. I watched that video more than enough times. And it's an old PSD in it anyway. And not for Highlander/Lexus hybrids.
P is P. Again, there is no forward motive force when in P. It is in D, either from traction battery, ICE, or combination of both. There may be SHAKE when ICE turns on, but not forward jolt. Unless OP used wrong description.
And it looks like OP bailed anyway to clarify.

Droid13

So help me understand...

When MG1 applies force to spin up the engine, there is an opposite force that is, as you mention "contained". In a regular car this containment I guess is just by bolting the starter motor to the engine block as there is a simple direct relationship between the starter gear and the crank gear. But I remember back in my young'n days driving a 1970 Toyota Corona with a manual tranny, no safety interlock on clutch. If I forgot to put my foot on the clutch and car was in gear when I started it the car when most definitely and violently jolt forward. I'm thinking MG1 is far more powerful than any normal starter motor and capable of far more violent jolts (if the force was allowed to transmit to the wheels).

So back to MG1, it spins up the planet gears but unless MG2 resists, the planet gears will just free spin without rotating the engine. I can understand in "P" MG2 is locked so the engine must spin. But idling at a light or otherwise moving at slow speeds, I can't see just the brakes or wheels providing the resistance (containment) to allow the engine to spin. I've always assumed (factlessly admittedly) that when MG1 spins up the engine, that MG2 simultaneous provides electrically the (hopefully) perfectly balanced counterforce to allow the engine to spin up with minimum "jolt". Otherwise, I don't understand how that much force is otherwise contained.

I've always guessed that any jolt felt was a slightly unbalanced application of force between MG2, MG1 and ICE resistance to spin up.

ukrkoz

And here is a bit more advanced animation from Toyoda on how this all works. Please go to minute 2. There is only one circumstance when "all units stop" is not applicable. That's when traction battery is depleted and ICE has to run to spin generator. But then, drive motor is not engaged. So not "jolt".
That said, there is no forward jolt with vehicle not moving, aka stopped, or in P.
That said, if you were in D, I stress this - in D, holding brake pedal slightly pressed to "just hold" the car and ICE kicks in - yes, there may be a noticeable forward tug, jolt, jerk, call it what you want to, as you have combined drive motor plus now started ICE torque applied during the system arranged in Drive mode.

Again, it IS idle discussion until OP chips in what he meant by "jolt". We are making assumptions here so far. Though it's good to have a refresher on what gear does what and when. Not really a practical knowledge yet..

salimshah

All the theories, but OP is missing to explain his observation(s).

Salim

salimshah

We all try to bring in information and at times some entertainment too. The key is how we handle disagreements. Once any person [who may be 100% correct] tries to prevail as if there is a duel going on, we get into problem(s).

I think the main purpose is to gather information and then let the reader decide what makes more or most sense to them.

So my advice is 'state your position' and then stop. The last post by any one does not need to be responded to.

Enjoy the reading (right or wrong). Even misleading posts can have some interesting bit of information.

Salim

salimshah

NateJG:
I recognize my error as my message was addressed directly and could be thought of as a public chiding. It was meant to lighten the situation and no more than a suggestion to take things lightly.

As an adult I have fessed up to my mistake publicly.

Talking about ........ or should I say inquiry about run-up number of posts, they have been accumulating over 18years with RX and then some with GS and SC. Yes, most of them have been useless .

Salim

wbrusseau

Thanks Salim. It mainly happens on each and every start; however, I've noticed at times when it is warmer outside it's not as pronounced.

wbrusseau

It clearly moves forward... If my foot is on the brake it does not move, of course. If the parking brake is on it sometimes moves, but not always.

salimshah

Thank you for the additional details.

My thinking was leading me to suggest to examine the engine mounts, but then you would have experienced more vibrational rattle.

The beauty of the gearbox is that torque from various sources can be applied at the same time. Power can be shared or taken from the strongest one.

Since what you are experiencing is odd, out of the box thinking may be required. For this you may like to acquire all relevant data for resident experts and Lexus trained professional master technicians.

Salim

vlad_a

There is a very slight "jolt" when the engine first starts from cold. I usually either keep my foot on the brake or have the parking brake engaged. That's pretty normal.