Jerkiness while sitting in park with parking brake on, anyone else experience this?

[BethlehemPrius]

Ok, I have sensed this a few times since i have had my car, but pretty much just ignored it, but is kinda odd, assuming it is just something with this different kind of tranny.

So the scenario, is that i was on a flat surface and just started the car up, it is still in park with the brake set, and my foot is now not currently on the brake pedal anymore. I felt almost like a very slight jerky motion almost like the car is trying to move forward a little bit, is this a sign of something wrong with the trans, or just normal for this car?

Everything runs fine on it otherwise, so figured I would ask if anyone else experiences this before going into the dealer to ask?

I have had this happen a few times but it seems to be hit and miss. Any ideas?

Thanks much!

[mgipe]

Is it the ICE starting up? On a cold car, the engine will start up a few seconds after you turn the power on, even if you are not moving or in Drive.

[NoSpam]

I have noticed the same thing. If you are sitting with the car in park when the ICE starts up it feels like the car wants to go. It feels like it is straining against the transmission interlock. If you have a foot on the ground and the parking brake off you can really feel it move around.

Regards,
NoSpam

[BethlehemPrius]

<div class='quotetop'>QUOTE(NoSpam @ Jul 20 2007, 07:01 PM) [snapback]482507[/snapback]</div>

I have noticed the same thing. If you are sitting with the car in park when the ICE starts up it feels like the car wants to go. It feels like it is straining against the transmission interlock. If you have a foot on the ground and the parking brake off you can really feel it move around.

Regards,
NoSpam
[/b]

Yup, that sounds exactly like what I am having also, it does happen when the ICE starts up, but it continues to do it while it is running till i put it in D just like you are stating.

Assuming its no biggie since it runs fine otherwise....

[Neicy]

I had similar questions before I got used to the car's behavior. If you search for "shake" or "shudder" you will find numerous posts on this topic. It seems to be more pronounced when you first start up from a cold engine. I noticed it also more on the first engine shut-down. At first I thought there was a problem but later learned that it is one of the little quirks of how the car operates. I can't find the post but I remember reading something about the engine always being in drive - or something similar. Come on guys; one of you gurus will be able to explain better than I can.

[SteveS]

<div class='quotetop'>QUOTE(Neicy @ Jul 20 2007, 07:26 PM) [snapback]482518[/snapback]</div>

I had similar questions before I got used to the car's behavior. If you search for "shake" or "shudder" you will find numerous posts on this topic. It seems to be more pronounced when you first start up from a cold engine. I noticed it also more on the first engine shut-down. At first I thought there was a problem but later learned that it is one of the little quirks of how the car operates. I can't find the post but I remember reading something about the engine always being in drive - or something similar. Come on guys; one of you gurus will be able to explain better than I can.
[/b]

Yeah, I've got the same thing going.

[craigk]

<div class='quotetop'>QUOTE(NoSpam @ Jul 20 2007, 06:01 PM) [snapback]482507[/snapback]</div>

I have noticed the same thing. If you are sitting with the car in park when the ICE starts up it feels like the car wants to go.
[/b]

Me too, happens only occasionally when I'm still in park, car moves forward and stops.

[steevr]

This happened twice now, once when I was driving and yesterday when my wife was driving. The car is in Park....you start the car and let off the brake. A few seconds later, the ICE kicks in for the first time and the car moves forward an inch or two. What's up with that?? When it happend to me, I thought the car slipped out of park.

Does anyone have an explanation on why this occassionally happens?? Should the dealer look at this??

Thanks.

[EZW1]

I have a thoery, but may be way off:

When a cold engine idles, it may idle rough due to the fact the air/fuel mixture is way rich until it warms up. The Prius engine electronics operates MG1 at a speed commensurate with engine rpm, desired wheel speed, and desired wheel torque. My guess is when the engine runs rough, the electronics has quite a job trying to adjust MG1 speed to keep the wheel speed and torque at zero. The result of this 'chase' scenario is the jerkiness you encounter. When you put the car in Drive, MG1 will compensate for engine rpm to provide drive torque and speed to the wheels. Since the car will likely be accelerating at this point, you will not notice the jerkiness because MG1's speed is constantly changing.

I notice a very similar symptom when I let off the pedal to transition from an acceleration mode to a cruise mode and feel the car jerk slightly.

I dunno, maybe I missed the boat on this one.

[efusco]

Originally Posted by steevr

This happened twice now, once when I was driving and yesterday when my wife was driving. The car is in Park....you start the car and let off the brake. A few seconds later, the ICE kicks in for the first time and the car moves forward an inch or two. What's up with that?? When it happend to me, I thought the car slipped out of park.

Does anyone have an explanation on why this occassionally happens?? Should the dealer look at this??

Thanks.

I think this is just the normal attempt of the car to move forward until the parking pawl engages the gear stop. I bet if you looked the car didn't even move an inch but rather the rocking feels more pronounced within the vehicle.