Hi Everyone,
I drive a 2011 G37 Sedan with about 36,000 on it, I bought it used. I have an issue that i'm hoping someone in here has experience with, because its very frustrating. Every morning when I first start driving or after the car has not been driven for awhile (such as in the afternoon after work) I get a stutter or a hesitation between 30-40MPH, which usually only occurs for the first few miles. After i've driven a few miles or for about 5 minutes its goes away and everything is back to normal. This occurs no matter if I floor the pedal or ease into it. I have taken it to 3 different dealers and none of them have said they have ever heard of anything like this occuring. I had my friend drive it who also has a G37 sedan and he feels it as well, but his does not do it. I also had a loaner from the dealer which did not do it. I did an ECU reset via the battery disconnect, but its still doing it presumably when the transmissions cold. Any help would be much appreciated.

 

I don't have an automatic G, but if I recall, there was a TSB for updating the transmission programming. Might want to see if that was done.

 

@OP

The dealer will need to do a proper diagnostic to determine what's happening. Sounds like this is easily repeated so long as the car is cold (ie not driven over night). They have equipment that will record a number of different parameters as the car is warming up from the cold state. A sharp tech who knows who to interpret these readings should be able to spot the issue.

If I had to guess, I'd say something isn't reading the temperature correctly.

 

When you say isn't reading the temperature, what exactly would you be talking about. Just so I can possibly bring up options when I go to the dealer. Trying a different deal this time.

 

I was generalizing above. I don't know all the sensors involved in the engine/trans control system. Based on your explanation, when the car is at operating temperature, the issue is not present. This suggests that the problem is during the transient period of full cold to warmed up. The ECU knows it's in a state of warm up based on a number of different inputs, several of them involving the engine temp (coolant), engine oil temp, trans oil temp, and probably a number of other factors. One of these inputs might be malfunctioning. Could also be some solenoid in the trans that's sticking.

The tech needs to scope the car during this transient period and then interpret the data to figure out what is not right. Similar to how a doctor takes an ekg or an eeg. You'll need to leave the car there for at least a day or longer.

Since the problem is easily reproducible, let them figure out. That's what your warranty is for.

 

Speak to the service manager and set up another appointment to leave your vehicle overnight and request another loaner.
Request that their top highly trained and most experienced tech hook up his consult lll and do a test drive first thing in the morning.

Let us know!

Goood luck

Telcoman