I purchased my 2011 IS250 in January of 2011, but only started to notice this problem about 6 months ago. What happens is, while braking the car seems to jolt and lunge forward. I initiallly took it to the dealership for my 5k service and mentioned this problem, but at that time it was only intermittent and they claimed they were unable to duplicate the problem.

A few months back I started notcing this problem more frequently, just about everytime I brake. So by changing my display to gear position I found that the jolt happens when the car downshifts from 4th > 2nd, skipping 3rd. Then when the car shifts from 2nd > 1st it jolts and lunges again. I brought this to the dealership's attention when I took it in for the 10k service, but yet again they were "unable to duplicate the problem."

Unfortunately, everytime I've taken this car to the dealship they've always given me an ES350 as a loaner, which of course doesn't exhibit this problem. After bringing it back home I went ahead and reset the ECU, but that didn't seem to have any affect on the problem.

Anyone have any ideas about what could be causing this?

 

You know what is causing it...you listed it already. The fact is you don't like the amount of transmission feedback it gives you while changing. Try snow mode, and see what happens. I'm sure you have a few hills in mind where it might be a good chance to use it instead of normal mode.

 

Mine does this as well. Yet it only does it when it's cold outside and the motor is cold. With mine, you feel it really down shifting kind of pulling you forward while your trying to stop. It's starting to get warmer here and it's not been doing it much.

 

Mine only does this in Sport Mode with aggressive braking.

 

There's a chance you might have ECT PWR on which can cause such effect to happen.

 

Hello,

I believe your problem may be one or both of...Electronic Brakeforce Distribution and Sport Mode. I have a 2007 and I believe it has some sort of brake assist or distribution feature. I have always noticed the brakes being a little "touchy". I believe this is by design so when you think you are barely pressing the brake the car seems to want come to a stop quicker than the amount of pressure you feel you applied. Thus it may feel that you are lunging forward when in fact you are stopping quicker than expected of the car feels a little "jerky". If you add Sport Mode into the mix then it's that much more "jumpy" if you will because now not only are your brakes "touchy" (by design) you are also dealing with some "jumpy" or "touchy" up/downshifting...again by design.

This is my opinion and experience so far after a couple of years so anyone please feel free to challenge what you see above. I'm curious to see if any other drivers have noticed something similar.

 

I never use ECT PWR mode; this always happens in normal mode. Also, the weather doesn't seem to have any affect on it. It has recently warned up here, and it seems the same as it was all winter. I've tried gentle braking, normal braking and aggressive braking, but I don't notice it with aggressive braking, perhaps because the car is screeching to a halt. I will give snow mode a try and see if that makes a difference.

 

I've had a similar problem since new. After the car has sat overnight cold and then driving in manual mode, it lurches forward from a stop when I take my foot off the brake. Similarly, when coming to a stop (still cold and in manual mode), the car jerks right before I come to a stop. The only difference here compared to yours is mine does it between 0-5 or 5-0 mph only. Sounds like yours happens at higher speeds.
I've had three different dealers look at this, but no one has been able to reproduce it (it's hard to explain to them, I think they are missing it) or give me an explanation. What's most distinct is it only does it when in manual mode... never in auto mode and only when it's been cold overnight.

 

Yeah seems to do it only when cold. On top of that I also notice this as well.

If you put on cruise control at 60-65ish km/h or 35-40 mph, and then you disengage it; you don't really slow down either, as if the cruise was still on but it is not. What I observed is that the RPM is a bit higher than normal and the 6th gear did not engage yet.

After the car has warmed up enough, above does not happen anymore.