[Vittorio Palermo]

I have a 2009 G37xS and this morning when I started it, the RPM went to1500 RPM and then back down to zero.
the whole car shakes and I can smell something bad from the exhausts.
Basically the car seems to stall but eventually does start when I give it gas

This only happens for cold starts and usually when there is snowfall the night before

What could this be? I have no check engine light either.
The car has 128,000 miles on it and maintenance is always kept. I use synthetic oil as well.

Thanks

 

[bachman]

I have a 2009 G37xS and this morning when I started it, the RPM went to1500 RPM and then back down to zero.
the whole car shakes and I can smell something bad from the exhausts.
Basically the car seems to stall but eventually does start when I give it gas

This only happens for cold starts and usually when there is snowfall the night before

What could this be? I have no check engine light either.
The car has 128,000 miles on it and maintenance is always kept. I use synthetic oil as well.

Thanks

That's a strange one.
You start out with "this morning" then say it does this on cold mornings/cold starts so it has been doing this or getting worse ? Any clues are helpful like it's getting worse or is just fine when the temps outside are warm or mild or the engine has already warmed up ....

Temps or cold mornings / cold starts might be a clue but I don't think snow is related. As to the odor, that doesn't sound like a good or healthy sign unless it's fuel and the fuel to air ratio is out of whack.

Has anyone worked on the car or changed anything lately? Something might have been done while it was still mild temps or warm out and the problem didn't come up til the colder weather. Bad gas ? Bad fuel filter ? I'm not sure what to tell you.

 

[TurboRev]

I've heard of this situation before from a friend and was told the reason was because the car was running really lean in fuel during cold starts. It kind of makes sense since you refer to the temperature. During a cold start, your car should idle at around 1,200 RPMs and gradually lower to around 700 RPMs as it warms up. If it goes lower than that, it could be the fuel to air ratio.

 

[TurboRev]

I forgot to mention that my buddy had the issue fixed by having an "idle relearn procedure" done at the dealership.

 

[racerx1986]

I would agree with turbo rev, take to the dealer and have idle relearned even cars have brain farts sometimes, Lol..

 

[bachman]

I forgot to mention that my buddy had the issue fixed by having an "idle relearn procedure" done at the dealership.

 

[bachman]

I would agree with turbo rev, take to the dealer and have idle relearned even cars have brain farts sometimes, Lol..

Except the idle re-learn is not a difficult DIY.... here is the procedure;

Infiniti G35 and Nissan 350Z resetting ECU, Throttle Release, Idle Air Volume Learning

These cars have 3 idle speeds. Mine is around 1200 to1400 at coldest start, 900 then about 650 to 700.

 

[Gilley]

The problem could be camshaft position sensors. The motor will sometimes stall but run rough when throttle is applied. A code is not always shown when this happens.

Also could be the MAF sensor needs cleaning, the throttle body needs cleaning and the idle relearn.