Hmm. This is weird then... I actually tested it this morning and drive is the one you need to sit in for it to drop a bit...

 

This doesn't seem odd to me as my car does this as well. I love the sound it makes. I usually let idle for 15-30 seconds and take off. I agree with the above poster that says it does this to get the fluids circulating.

 

Exactly what my car does. We have nothing to worry about. Although I have a 5AT so dropping it from park to neutral usually lowers my rpm's a bit, and engaging drive even further so.

 

I was researching these exact issues and found this thread.

The above original post describes behavior of my 2008 G35 6MT with 58000 miles perfectly. And I agree, it was not like this before. I have had it since new so 13 years now. I know car well. I have also done IAVL relearn (make sure your battery is fully charged first), accel pedal released position relearn, throttle body closed position learn. No change/improvement. My cold starts especially if parked outside, rpm hits 2400-2600 even. I have even seen rpm go up to almost 3000 once. I tried, as another post mentions, to let clutch out, even with hand brake on: no change. This could actually be dangerous while maneuvering your car out of a parking space with your engine at such high rpm. Car tends to jump more when you let clutch out at these rpm's. I was just experimenting to see if I could find a way to bring high rpms down quicker on cold starts. My standard start up sequence is to let 30-60 seconds elapse until engine rpms drop to 1200-1400rpms before I start moving/driving car. Nothing I have tried will bring high idle down: depressing clutch, putting trans in gear, letting clutch out with parking brake on.

Second issue observed in original post: clunking when releasing throttle, without pushing clutch in, using engine braking to help slow down, I get same noticeable "clunk", as if fuel supply was cut off altogether. Car resumes normal operation once I depress throttle. Only way around this i have found is to let foot off gas very progressively, but there isn't always time to do this and you should not have to do this. I wonder if rubber bushing that restrains rear differential has gone bad, causing this issue. Will check next time under car.

In summary, I could have written original post as it matches my observations with my G35S 6MT exactly. Mine did not start doing this until after 12 years of driving it. Only in years 12 and 13 did these issues start. I pay attention to details with my cars, so you have to trust me on these observations. I take care of my cars. I still get compliments on my G.

My car is mostly stock. Not sure what condition was of original poster's 08 G35S 6MT was.
After 10 years, I installed Fast Intentions cat back exhaust. None of the above issues occurred after this install.
After 11 years, I installed High flow air filters and RJM Performance clutch pedal assembly: best change ever. Makes releasing clutch from stop and shifting much smoother. Clutch feel/action should have been like this from factory. (I installed cat back exhaust to increase volume so I could hear engine better when working clutch in effort to reduce stalling and smooth out my shifts. It helped a bit but RJM clutch nailed this problem.) None of the above issues occurred after these changes.
After 11 years 4 months, I had an UpRev tune done on chassis dyno by an experienced tuner. I always wondered what a performance tune done properly on a chassis dyno would do. On a mostly stock car, not a whole lot. Tuner even warned me not to expect much but I was curious and decided to have it done anyway. None of the above issues occurred after this tune.
After 12 years, at 56700 miles I cleaned throttle bodies because my idle was unsteady and dipping low enough to even stall once. After performing relearn procedures mentioned above, warm engine idle returned to a perfect and steady 650rpm.
A month later I cleaned the MAF sensors with CRC MAF cleaning product. I read all instructions and followed them. I got this at same time I got CRC throttle body cleaner but wanted to do each task separately in case any issues arose, to help know what the cause was. No issues observed initially. But a while after I started to notice higher idle on cold starts. I thought maybe I damaged one of the MAFs when cleaning them. So I bought a new one (not inexpensive) and am now experimenting with swapping MAFs to see if this takes car back to the way it used to operate. So far I have only swapped driver side one: no change. I will install 2nd MAF today to see if this changes anything and post my results here. (borrowing second MAF from my 2009 Versa with only 28000 miles, same p/n MAF. I will then try each of the G35 MAF's in Versa to see if Versa behaves differently.

In summary, high idle is normal when cold. On my 2009 Versa, it cold starts around 1400-1500rmp. Not 2400rpm+ as I now experience with G35. My G used to cold start around 1400-1800rpm but never over 2200rpm. So I think something is not right. But I have not found out what yet.

 

If it idles high when cold but normal when it's hot it's probably just the idle air algorithm. Are you 100% SURE you followed all the pedal dance steps properly, including ALL the prerequisites listed in the FSM?

If you have a bluetooth OBD2 adapter and an Android phone you can do the relearn with the click of a button using the Nissan Datascan app, I believe the NDS3 app has this functionality just like the NDS2 app does for the V35 chassis.

It's easy to screw up the last two steps of the idle air relearn if you're using the pedal dance method: Start engine, then LET IT RUN FOR 20 SECONDS. You must use a stopwatch.

 

My car has been doing this since new also, I have never liked how high it idled when very cold, ( I mean who revs a cold motor to over 2400 RPMs?) its one of the reasons I have always put in 0w-30 oil, to help with oil that is not so thick, so it gets moving to the top of the motor, that's revving itself silly! Once warm, and hot then yes it's around 700 RPMs. Almost 78,000 miles on mine.

 

Ahh ok I thought it was something that happened recently, to be honest I don't think I've ever looked at the tach while mine is warming up to see where it was at. I usually just fire it up and go back inside to eat breakfast...

 

HI Cleric,

Yes I am certain I got IAVL working properly, using stop watch on my lap top and having re-written instructions to know what to do at what number of elapsed seconds. I can now do IAVL repeatedly, reliably with pedal dance method. Also, I can tell it is working because when in learn mode, i watched idle go from 900-1000rpm down to 650rpm, progressively. Afterward, my idle when warm is 650-675rpm.

Initially, I could not get IAVL to work. In my case, reason was I assumed my relatively new Infiniti service part battery would meet voltage requirement for IAVL process to work. I was so sure, I didn't even check it with volt meter. This was a mistake. It turns out my battery always seems to be a bit below the 12.9V threshold. So now, I always put battery on Battery Tender charger night before doing IAVL to insure battery is fully charged. I was actually doing IAVL process correctly but since battery voltage was below required threshold, I could never get learn process to start. Very frustrating.

Your other question about OBD2 scanner: I have one, OBD Link MX+ with Nissan/Infiniti add on Enhanced Diagnostics. But... I have an iPhone which NDS is not compatible with.

 

Hi Triton,
Glad to see another forum member that has been around longer than I have!

The cold start high idle (over 2200rmpm) on my car only started after 12+ years, after cleaning throttle bodies and MAF's. Prior to that high idle cold starts (2400-3000rpm) did not happen. Worse part is colder it is , higher it revs. I agree with your concern about revving an engine that high on cold starts. This is not right. However, I am not saying that cleaning throttle bodies and MAF's caused this problem. I have no proof of that. But I can say that my excessively high cold start idle problem started after I did those tasks... carefully.

 

Update on Swapping out MAF's:
I have now swapped out both MAF's for one new one and one from my Versa with 28000 miles on it ( I decided not to clean it lol!).
My G runs the same: High idle when cold, runs OK once warm. Still have clunk, on deceleration when lift foot off accelerator, as if fuel delivery is being cut off or something.

I also put each of the G35 MAF's into Versa and confirmed Versa works OK with both of them.

So this issue is not caused by MAF's. I did not damage them while cleaning them.

I wonder if I disconnect the battery overnight if this will ah... re-boot(?) the ECM and maybe it will run differently, eliminate excessively high cold start idle and deceleration clunk? I never do this because I don't like loosing all the memory settings for seats, mirrors, radio, auto down windows etc... but might be worth a try(?)

 

Doing an ECM reset (disconnecting battery then pumping brakes to discharge the system) is only going to reset your long term fuel trim.

Might be worth a trip to Nissan/Infiniti for a diagnostic just to see if Consult-III can find anything wrong that might be causing that.

Here's what I suspect, you probably have a minor vacuum leak that goes away once parts heat up and expand, a vacuum leak will absolutely cause a higher idle.

Good tip about throwing the battery charger on the system before doing the idle air reset.

 

Hi everyone!

i have the same issue on cold start. 2.000-2.100 rpm . did anyone solve the issue?

 

I changed my intake filters, repaired an exhaust leak and after a reset and relearn it seemed to help.

 

intake filters are new. what type of exhaust leak did you have?

 

That's a normal cold idle rpm, it should drop down to 650 +/- 50 in park while the engine is up to temp.

It should only hang at above 2000 rpm for maybe 10-15 second until it starts to creep the idle down in 100rpm increments while it warms up.