Lurching while stopped

[Dad]

As you have probably gathered this is fairly common and it only occurs briefly after first starting up. While it is annoying, it looks to be of little concern. You are wise to post here to get other's opinions and feedback. Always better to be sure about these issues.

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[CurtisB]

I haven't had issues with him............

 

[NedF]

Exactly. More prominent when the engine is cold/warming up, as the RPM and torque output varies a bit, which the traction motor can't react fast enough to counter. For my '23, once the engine is warmed up, I don't notice torque surges.

If you researched how the eCVT worked like I did > This makes perfect sense! I do not under stand why I did not figure this out on my own

 

[Pikey87]

I've just accepted it as a quirk of a built to cost hybrid lol. The emissions recall reduced it, but it still does it occasionally. Like most others, I notice it the most when the engine is cold. I'm not worried about it personally.

 

[TedTX]

I have also felt it on my 2.5 week old MY24 and like others have said it is usually the first complete stop at a light with a cold motor.

Could be a different cause, is it more dramatic then braking and occurs on same conditions on gentle acceleration? Hybrid only.

 

[hdave]

Same here.
Glad to hear it's not just me.

 

[Sykotyk]

I have a 22 Lariat Hybrid. It does this from time to time. Did it yesterday so it was fresh in my mind when I saw this post.

The issue is that when the engine is running, the transmission gears are spinning EXCEPT the one providing power to the wheels. Only thing holding you still is the mechanical brake. But in addition to charging the battery, there is still some 'push' of the gears that is stopped by the mechanical brakes. It feels like waves, to me. Light, barely noticeable surges forward. You really notice it if you just barely press the brake pedal.. As I have a tendency to do because there's not much else happening with the vehicle usually to propel it forward, so light application of the brakes is all that's needed. Except when the engine is charging up the battery. So, you forget, and you feel the surge.

I've never once considered it an issue. More of just an annoyance. Because of how the vehicle charges, I don't think there's any way to completely 'de-link' the transmission from the drive wheels. There is no clutch. Just which part of the planetary gear assembly is spinning.

 

[The Real Maverick]

I guess that makes sense because this transmission doesn’t have any clutches. To idle the gas engine at a standstill it needs to spin the electric drive motor backwards at just the right speed to match and it probably can’t hold the wheels dead still at 0 rpm with the engine running.

It's a little bit of this, yes.
If you put the wheels up on jack stands and put it in neutral with the gas engine running the wheels will (usually) spin a little. There's no disconnect. So it's a fine balancing act. With no static resistance on the wheels, they will spin a little bit. It's hard to have zero torque among rotating parts in a 3 way powered transmission.

With gas engine spinning and generator spinning it's only natural for the traction motor and wheels to want to spin a little.

 

[dlhort1955]

My EB just did this yesterday. I backed up to the garage, put it in park, turned off the key and it lurched back and forth twice. Just so weird. Hope it does not do it again.

 

[The Real Maverick]

This is different phenomena in Hybrids.

 

[clavicus]

I think I can relate about the cold engine being part of the pattern. Mine is pretty subtle, where I can obviously feel it but it's not actually luuuurching my car forward. It's like I feel it through the brake pedal mostly. Doesn't happen often. I'm a year 2022, one of the first Hybrid builds. Hasn't gotten "worse" as far as I can tell, just a little quirk once in a while, from my perspective.

 

[Silver23]

Does it to me on the first stop on a cold day. (usually)
Looks to be "normal" by all the posts here.
I certainly won't take it in for service because they will NOT find it, and even if they did it won't get fixed.....guaranteed.
There could be an update to bump the idle when cold or something some day but I wouldn't count on it.

 

[stevj]

Mine does that when the engine is cold and idle is a bit unsteady. So I start off in SPORT or TOW/HAUL mode so the engine will run and, once the engine warms up, no more surging and I'll switch back to NORMAL or ECO mode..

Steve

 

[MaveRichard]

I have been watching the ignition timing during these events over the last few months. When the ICE initially starts the ignition timing is pretty severely retarded (~12*) then you can hear the tone change after about 30 seconds of running to 12-24* of advanced timing. I have seen as high as 45* of ignition advanced during normal operation.

The surging only happens when the ignition timing is retarded. I know that this is done to warm the primary catalytic converter more quickly.

I am sure that the variable cam timing is involved here, I just haven’t watched it… yet.

 

[stevj]

That change you see at 30 seconds may be the ECU switching to closed loop mode once the O2 sensor heaters get them properly warmed up.

Steve

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