Hi I have an automatic G35 coupe 2005 and my car randomly died twice while waiting at a light. I decided to clean my TB and MAF as I was installing a new plenum spacer. I haven't had a problem since until now as the problem has happened again. I cleaned my MAF sensor today as I felt I didn't clean it properly before and yet it died. I followed videos online that told me to do the idle relearn and ECU reset so I believe it shouldn't because of that. My guess is that maybe I have a vacuum leak but my car seems to drive fine and no CEL.

 

I'm still pretty new to the G35, but it seems like there are a lot of things that can affect the idle like that where it is dropping too low:

1 - vacuum leak - check every hose for hardness and even small cracks in the hose, like PCV and it's hose, the hose that leads into the air intake
2 - Valve cover to valve cover hose - if cracked this can affect it.
3 - valve cover gaskets AND the spark plug gaskets - I see a lot of people change the valve cover gasket and not the spark plug tube gaskets, and you can often see they have shrunk enough to cause a small leak.
4 - intake manifold - I don't think the metal gasket is usually the problem, but the bolts could possibly be not quite tight enough
5 - Upstream air/fuel (o2) sesnsor - When these get lazy or are almost dead, at least in my experience, no error is thrown, it has to be really dead to error out. So for this one, I would see if you can read live data to see how lazy it is before replacing.

These are the primary items I have found besides what you have done. Cleaning the MAF and the other items you have done all make sense as well.

It seems that with these cars, no CEL doesn't mean everything is fine.

Good luck.

 

Would any of those problems cause rough idle or other small symptoms. I’ll check my hoses but not sure how I could check my gaskets without fully removing all the parts out, which is the last thing I want to do in order to figure which part is going bad.

 

When the car is idling, turn the steering wheel, do your rpm's drop or do they hold steady?

If they drop you probably have a failing power steering pressure sensor.

Otherwise I would suspect a vacuum leak causing the car to stall. Check the PCV hoses and valve.

 

ah yes I noticed that my rpms
would move when I would lock my steering wheel left and right.

 

so I just checked my car today and so far after the ECU reset from disconnecting the battery. I haven’t witnessed any stalling for the past few days. And about the power steering pressure sensor, the rpms don’t drop below 600-700, if anything it goes up abit when I lock the steering wheel, is that normal?

 

Yeah it should raise the rpm just a little to compensate for the extra power needed to turn the steering rack. That's normal, it's when the rpm's DROP that you have an issue.

There's also an idle air algorithm that might need to be reset if the idle rpm isn't correct. 650rpm +/-50 at idle.