Strange idle or transmission problem. It’s hard to stop smoothly when coasting to a stop sign or while in stop & go traffic. The RPMs jump about 400. Makes it difficult to come to a stop. The idle is perfect while parked and it doesn’t stall.

it appears to be worse when the AC is running.

The 06 G35 has 120k miles & I just serviced almost everything..I put new Nisian double platinum sparks, drained & filled transmission fluid twice with Nisian Matic-S ( the fluid level is perfect) , cleaned throttle body, replaced with new infinity gasket & did all the relearn steps . New air filter, new cabin filter, new wager breaks, changed to Mobile 1 5w30 synthetic, changed diff gear oil, flushed coolant with Nisan green.

any suggestions please!

 

Rpm surge is usually a vacuum leak. Since it is doing it more in relation to the brake pedal start looking at the brake booster and it's vac line.

 

There is a check valve up inside the hose near the booster that might be failing as well.

 

^^ probably a vacuum leak, could also be MAF? other people complaining about surges have found replacing/cleaning their MAF to be a solution.

but as cleric said since you notice it while braking, most likely one of the lines he mentioned. gl

 

Thank you guys, could it be my throttle body by any chance? When I cleaned & opened butterfly kind of herd a unwinding spring noise.

 

Yeah, you can't clean the throttle bodies on these cars without being very careful. The G/Z are hypersensitive to throttle body settings. Trust me, I made the same mistake on my first G35.
The only way to do it is to have two people, one person holds the pedal down WOT (engine off of course), and the other person cleans the throttle bore.
If the throttle body made a weird noise, that could be an issue.

Try the idle re-learn procedure, that could solve your problem.

 

Also, make sure you bleed your cooling system correctly. These cars are a pain to bleed.
Tell tale sign you have not fully bleed the cooling system is if you don't have heat at idle.

 

I should have thought of this too!

When putting in my spacer I accidentally cut the coolant line going to the TB (another story) so I drain and filled the coolant. over the course of bleeding it the RPM surged a lot and I was scared to drive it till i bleed it all the way. took me a couple days because car takes forever to cool back down to complete the coolant bleed procedure. if you open the bleed valve and the tube looks dry asf try performing the bleed

Edit: when he says heat he means turn your heater on full blast in P (when at operating temperature) and rev to 2k~ for 10 seconds

if your face isn't melting off, there's air in the system

 

Confirmed: break booster hose & filter is ok. Coolant test with heater passed. I did hear hissing at PCV valve hose & got louder with wiggle. I replaced PCV Valve & PVC hose today. Also did idle relearn again. Still have the same problem. I did notice RPM bounce when I let of the gas and lower speeds and when letting off gas coming to a stop. Breaking also causes the RPM bounce.

I’m thinking next step is Throttle body. I have a felling I screwed it up when I didn’t disconnect battery and when laid it down to spray I did hear that spring wind sound also opened butterfly. It’s got plenty of tension. But maybe the TB is letting improper air through at certain times or possibly messed up something electrical wise. It’s only $150 for hitachi on Amazon & I’ll get a new MAF at the same time. Last resort is to take it to the stealership for flashing software, they want $160 for that service. What do you guys think?

 

darn, yeah always remember to unplug batter when touching any electrical

could keep trying the tb relearn, as it is very hard to actually get down. even if you do all the steps seemingly correct, there is a lot of room for error

if it still is bad after that and you've tried everything else, infiniti it is. although i would try explaining the problem to them first to see their opinion before asking for a flash

 

FYI it can be quite stubborn/finicky to do the idle relearn. After I cleaned the throttle body on my first G, the idle was hovering at ~900-1,000. Make sure you do it with ALL accessories turned off. It took me 3 or 4 times the first go round to finally get the car to 'learn' the correct idle speed. What I ended up doing was taking my phone & watching that vid (linked earlier) and doing the procedure in unison with the video. You can also do the idle relearn with DataScan II, which I recently invested in. Worth the money in the long run for me personally.

Check the intake hose couplers for cracks, as well as the EVAP hoses behind the plenum/throttle body area. Both of my G35's had cracked intake couplers when I purchased each car. If they are cracked, that can cause the engine to run lean, which could be causing your idle to surge. Any air that gets into the engine that isn't going across the MAF is unaccounted for, thus the engine gets more air then the ECU thinks its getting. If your couplers are bad, you can get silicone replacements from Z1 and now ConceptZ. ~$35-40. The stock intake and couplers are only sold as a set from Infiniti, and its $200+ from the dealer last I looked.

 

Might have to invest in a DataScan II

funny enough i did a valve cover swap on my g this weekend. broke the breather hose and had a silicone replacement overnighted from Z1. installed it and started to put the intake manifold back on. well i ended up breaking the PVC valve hose :-)))) so thats coming in too now

lesson is, our cars are reaching that time where componants really start to wear, whether the car has 40k miles or 200k miles. best bets right now are vacuum leak or the tb. try to rent a vacuum leak kit from oreillys, autozone, etc. cannot provide advice on that though because i have never done one, although i should

 

Did you end up fixing this? I’m having the same issue and can’t figure it out for the life of me

 

Sounds like a failing brake booster. Turn on the engine, pump the brakes a few times, turn off the car.

Wait 5 minutes then disconnect the vacuum line on the brake booster it SHOULD hiss and suck in a bunch of air because it should still be under vacuum.

You can also hook up a handheld vacuum gauge and pump in vacuum pressure and watch for a drop, it should hold vacuum for 5 min.