I have an '09 G37x sedan. After driving for 10-15 minutes, the car starts to shudder right around 2200 rpm, and no matter what won't let me accelerate above that threshold. It feels like driving on a washboard.

Same thing happened in December 2009 and January 2010. I had it in for service and they could not recreate the problem, but reset the computers and replaced a filter. The problem went away for just over a year but happened again earlier this week. I sent it in for service and they again can't recreate the problem.

The difference now is that in addition to not going above 2200 rpm, it was jolting strongly on the downshift. It felt as if someone had jammed on the brakes.

Anyone have any ideas, or ever hear of this?

 

This issue usually happens when the ECU goes into limp mode. I see the same type of threads pop up every winter. For some reason it happens more often in cold weather.

 

yep, limb mode for sure.
The car do that when something went wrong.

 

what exactly is limp mode? and why does it happen?........I'm trying to help my dealer out because they can't re-create it (or have any theories as to what the problem is)

thanks

 

I'm sort of a novice car enthusiast, but from what I've heard...limp mode can be caused by overheating or O2 sensors detect something and freak out.