Had something weird happen the other day...well weird to me at least. Started the car(engine didn't start)...released the parking brake and placed it in drive. The whole time with brakes applied. Was checking a message which just dinged on my phone when the ICE started and the car lurched ahead even while brakes were applied. It moved only 3-4" but startled me nonetheless. Anyone have this happen before?
Due to the engine orientation, a strong torque when the ICE starts causing the vehicle to lurch/rock a bit is most common when it happens in park. At speed, you don't notice it because the rest of the dynamics dampen the effect by transferring the torque to the rotating wheels. If the main brakes are moderately to firmly applied, you should notice the vibration but not any wheel motion. Perhaps the brakes were only applied lightly, allowing some slippage with the unexpected torque?
Yep. I've had that happen several times. When I am in a drive-thru lane getting coffee. The ICE will suddenly start up and shake the car and startle me. If I'm not in park, with just my foot on the brake the car seems to lurch forward a few inches.
3-4" sounds like a lot but this is "normal". As wrprice said, the torque required to start the ICE causes a counter torque at the wheels. On my car (Gen3), I also notice that when it's in park, the car will apply the brakes just before ICE start, and it still moves a tiny bit. My ScanGauge even shows a counter-torque being applied to MG2 during starup, and then to counteract the torque of MG1 acting as a generator. I suspect two things happened to you to cause an exaggerated movement on ICE start. First, you were in D with the brake applied, so the car probably didn't apply the brakes harder. Second, the car is likely guesstimating at the counter-torque required for starting a cold engine (inertia effects will vary based on how fast the engine spins up) and probably got it wrong. Also, unexpected movement probably seems much greater than expected movement.
3-4" seems a bit far but I've had it lurch if my foot wasn't placed firmly enough on the brakes at a traffic light and the engine kicks in. A good reminder to myself to ensure my brake pedal is firmly depressed
Wherever the tyre touches the road it's always, always stationary. Only the parts not in contact with the road are moving! Think about it.
Apparently there is another reason to plant your foot too. If the foot is not firmly planted, the battery is still sending power to MG2 Yo can see it on the gauge too. See ScanGauge II – Prius Gen 4 XGauges – Observations on Hybrid Battery Current | PriusChat
Probably more give in this new rear suspension. I've only noticed a slight lurch after I release the footbrake when I forgot I've got the foot operated parking brake on and put the car in drive, this reminds me I'm trying to drive off with the parking brake on Doh!
The very first time my car lurched, it almost hit the car in front of me! (I was in the drive-thru lane getting food.) I think my Prius jumped a foot. And yes, I was too close to the vehicle in front of me, and yes my foot was barely resting on the brake. Not a good combination! I went there, I conquered, I learned. Just another Prius oddity... Now I just use the (P) button when I'm stuck in those lines.
Perhaps it was saying "Enough weight already!" Finally got our first snow here. 7.5 inches measured. We expect another 1.5. How is your weather, CC? Still raining? Keep safe, everybody. I will wait for the neighbors to plow the road & driveway before trying a drive. The 2 neighbors have a competition plowing with their tractor blades.
My back hurts! Try squeezing a football player size man into a small Prius! What was I thinking when I bought that little Disneyland car!?
