I have a 2007 G35, with around 34k miles on it. Recently it has started having problems: hesitating after it has been sitting cold. I go through the normal process of letting the car go to under 1k RPM or so, and just to make sure that its warm enough I've let it go all the way to the half-way mark on the temperature scale, where it normally sits.

Basically what happens is, after I start off... initially there is no hesitation. I notice the problem starts happening after the first time I stop completely, be it at a traffic light or anything. Then when I go, by accelerating normally, and the RPM hits around 1400-1600 RPM, it loses power like I took my foot off the gas for a split second, then jumps back up, then falls till I cross around 2000 RPM. As I drive, it starts to smooth out, as in there is not as much loss of power, but I still notice that very slight hesitation. After about 4-5 minutes of driving, its gone completely. Now, I can make this effect go away faster, if I accelerate faster than usual, by pushing the RPMs up to 4-5k starting off. One other thing... I noticed that if I don't stop, but instead go up a slope/incline, it happens right away (considering I only push it to around 1500 RPM), unless I fly up that ramp, which I don't want to do for obvious reasons.

I had it checked by Infiniti who just did a thorough check with their computers, but nothing showed up. They recommended I change the air filter, which was done, and the oil has been changed regularly as well.

Has anyone seen this before or have any idea what may be happening?

TIA.

 

Happens to my 2007 as well and many other people on here. Nobody really has a clue on why it happens.

 

Well that sucks. Sounds like a defect if other people are seeing it too. Blurgh!

 

I can say the same thing.. my car does it as well. if I get on it. it looses power.. then it seems to catch up and then takes off hard, but what I also tried is turning the traction control off it still hesitates but not as much as it did while the traction control is on.

 

Maybe you need a ECU upgrade from the dealer or one of your MAF sensors aren't working right.

 

Found a technical sercvice bulletin related to this:


Classification: EC07-008A

Reference: ITB07-045A

Date: April 27, 2009

2007 G35; COLD ENGINE START ISSUES

This bulletin has been amended. The Claims Information has been updated. No other changes have been made. Please discard all previous versions of this bulletin.

APPLIED VEHICLE: 2007 G35 Sedan ONLY (V36)

IF YOU CONFIRM:

Drivability issues as follows:

^ Rough idle during the first minute of engine operation after cold engine start.

And/or

^ Slight engine speed fluctuation during light throttle acceleration during the first ten minutes of driving after cold soak.

NOTE:
This issue, if it should occur, is related to engine temperature. It is NOT related to ambient (environment) temperature.

ACTIONS:

Confirm this bulletin applies:

^ Check and compare your Current ECM Part Number to Table A.

If that part number does not match one in Table A, this bulletin does not apply. Go back to ASIST for further diagnostic and repair information.

If applicable, reprogram the ECM.

NOTE:
To help ensure smooth engine performance, 5W-30 oil must be used in this engine. DO NOT USE engine oil with a thicker viscosity than 5W-30 in this vehicle.

 

That just might be it! Glad its just a software issue. Will have it checked out some time this week or early next. Will most likely take a print-out of this to the dealer.

Thanks!!