Yaris mk3 shaking in P

[JCT-DK]

Hi. 

When starting ice at cold by pushing the accelerator with gear lever in P i notice that the car or engine is shaking and making the car rock a little back and forth. 

It's just for some few seconds then it stops. Is feels like there is a slack in the P position. The hand breake is released. 

I am worried it could be related to an egr issue making the engine vibrate. I not hear any knocking from the engine. 

Anyone had same kind of experience? It doesn't seem normal to me. 

Greets 

JCT

 

 

[Bper]

Hi Johannes,the rocking sensation you feel along with the shaking during cold start could be caused by a couple of things in addition to the engine vibrations mentioned earlier. 

Engine mounts are designed to absorb engine vibrations and prevent them from being transmitted to the chassis. Over time, these mounts can wear out and become less effective. When this happens, normal engine vibrations, especially during cold starts when the engine runs a little rougher, can be more pronounced and cause the car to rock slightly.With an automatic transmission the rocking sensation could be related to the torque converter. When you press the accelerator in park with an automatic transmission, the torque converter tries to engage and transfer power to the wheels, even though the car isn't moving. This can cause a slight shuddering or rocking motion in some vehicles.

I would check the engine mount condition if you can't do it yourself a garage can inspect the engine mounts for signs of wear or tear. If they're worn out, they'll need to be replaced. Avoid revving the engine in park it's generally not recommended to press the accelerator in park for extended periods. This can put extra strain on the engine and transmission, potentially amplifying the shaking and rocking sensation.

If the shaking and rocking are severe or persistent, it's best to get your car checked by a mechanic. They can diagnose the issue and recommend repairs. 

Are there any other symptoms accompanying the shaking and rocking, like unusual noises, check engine light, or sluggish acceleration? These can help pinpoint the cause more precisely. If the shaking and rocking are very mild and only last for a few seconds on cold start, it might not be a serious concern. However, if they are severe or worsen over time, it's best to get it checked out.Hope this helps.

 

[MikeSh]

2 hours ago, JCT-DK said:

It doesn't seem normal to me. 

It's normal for a hybrid.

[JCT-DK]

So nothing wrong with this behavior? 

Some shaking is okay? 

I learned the colder and the higher state of charging the more the car shakes. 

Should I apply the handbrake? 

[Cyker]

I don't know about the Mk3 hybrid, but the Mk4 is quite vibraty when it is stationary and the engine is running to charge the Battery. I assumed that was because the 3-cylinder engine in the Mk4 isn't balanced, but not sure why the Mk3 would since that has a 4 cylinder engine...

[MikeSh]

1 hour ago, JCT-DK said:

So nothing wrong with this behavior? 

Some shaking is okay? 

I learned the colder and the higher state of charging the more the car shakes. 

Should I apply the handbrake? 

If it is a hybrid (you haven't confirmed) then the engine is started by MG1 spinning it hard against the stationary wheels. As you've found this makes it 'bounce' against the P pawl where there is some play leading to the rocking back and forth you describe. Applying the brake, better the foot than hand as the former will hold the front wheels, should stop this.

[JCT-DK]

Sorry I forgot. 

Yes it's a hybrid. 

[JCT-DK]

So this behavior is harmless? 

Perhaps the yaris doesn't have sufficient self weight hence it oscillates a little when the MG1 is working at it's hardest. 

[MikeSh]

2 hours ago, JCT-DK said:

So this behavior is harmless? 

Perhaps the yaris doesn't have sufficient self weight hence it oscillates a little when the MG1 is working at it's hardest. 

It's just how the system works. MG1 is mechanically in between the engine and the front wheels, sort of. So when starting the ICE MG1 is effectively pushing the engine one way and the reaction to that is that it pushes the wheels the other way. It only takes a fraction of a second* so this force disappears immediately. 

The result is that the car has been briefly pushed in one direction against the pawl and then released, so it bounces back until it hits the other side of the slack and probably then bounces again. The flex in the engine mounts likely also gives some spring to it.

( * MG1 is not a little !Removed! (#) like a normal starter - more tiger like. Ordinary starters turn the engine at 200-300 rpm but MG1 spins it at about 800, so it starts instantly, and that means there is a lot of force involved.)

( # Snowflake filter 🙄 . You can probably guess what was there.)