Like many with the vq35hr, I've had the following issues that started presenting at about 90k with no CEL:

1. Stuttering/low idle/near stall/stall when stopped in gear
2. Upon warm restart, engine idle would drop below 500 rpm and almost stall,
3. When cold, at light throttle input, a stumble/stutter around 1,700 rpm that almost felt like a transmission slip.
4. When cold and in 5th gear but low speed of around 40 mph, the car actually bucked.

Thanks to many of you and our other Nico owners across the web, I can tell you the following steps fixed all of it.

1. Clean the throttle bodies with throttle body cleaner. Used the method of disconnecting the negative battery terminal and removing them but leaving the electrical connection intact. They were, as expected, filthy.

2. Vacuumed out the air intake boxes. Turns out I had an oak leaf the size of my hand in the right side intake box I'm front of the filter, which explains why resetting the ecu fixed the problem in the short term but it always eventually came back. The system was trying to compensate for a lack of air but could only do so much.

3. Cleaned the MAF sensors with MAF specific cleaner.

4. Pressed the brake a few times and the left the negative battery cable off for 24 hours.

5. Did the on/off pedal dance for open and closed idle relearn.

Call it luck, voodoo or overkill, but it worked. Car runs better than the day I brought it home last year. The torque curve feels smooth and linear.

In total it was probably 90 minutes of work and about $20 in supplies. I used to turn wrenches in my youth but am pretty rusty- someone with more experience could probably do it faster. My indy mechanic suspected transmission failure (love them and trust them, but they specialize in Mercedes, BMW and Land Rover/Jag, so I don't take them as gospel with this.) Plus the thought turned my stomach (I've had 3 Infinitis and had one transmission replaced under warranty in my 2000 I30.)

Couldn't bring myself to take it to the dealer and pay them to not figure it out.

Thanks to all of you for your combined wisdom!

Long story short, clean your throttle body and make sure your air filter isn't clogged?

XIS, yeah, pretty much. As you might have figured out I'm not great at brief, brilliant and gone.

I also had to string it all together myself so I figured maybe someone else could benefit from the path I took. It was also a personal vendetta of mine to solve this issue. Looking to get 150k+ from this thing.

I just ordered myself some plugs and plan on cleaning the throttle body for the first time also... 88K miles... Looking forward to a bit more responsiveness and MPG!

Well this is the perfect thread to continue talking about this DIY maintenance / tune up.... I scared myself a little after I finished, then called the dealer and they scared the s*** out of me! Ready for a long, short-story?

Got myself the OEM plugs, throttle body and MAF cleaners and then started my adventure. It is more than hot here in the Desert right now, so I tried to do a little the night before to get a head start.
removed my K&N' filters and sprayed the cleaner on them, washed out the dirt and crud and then re-oiled..let them sit.
Unplugged my negative battery terminal.
Removed the MAF sensors too and gave them both a good squirting...I let them dry overnight also.
Removed the hoses and got to the throttle body. Soon realized my allen-head wrenches were beat to hell and some rounded corners, so I went that night to get a new, nice set.
The next morning, I removed the throttle bodies and they were MORE than disgustingly filthy. No wonder my car was doing the start/stall thing every once in a while and my MPG had dropped to 17. Gave the driver's side TB a good cleaning. (maybe too good?) I had read conflicting info on the cleaning technique and if you were allowed to move the butterfly valve or not. Needless to say, I moved the hell out of it and scrubbed that sucker clean (thank you, OCD)
Next, went to remove my plugs and thanks to my ricer sons and their constant engine/exhaust/wheel changes/coil-over adjustments and camber tweaks, they had 'misplaced' my extensions and my deep sockets.. so back to the store. Got a super nice extension set and some color-coded deep sockets. (14mm for our skinny plugs)
Removed and replaced the plugs. All removed nice and easily and all looked like they were definitely ready for a change.
Repeat the process on the passenger side.
Put the puppy back together.
Start her up.. something is whacked... no throttle response at all.. It has to be a silly connector that I didn't get clicked in all the way... Took the engine cover off and YEP - passenger side TB connection wasn't fully connected. So I re-connected it.
Start her up again, definite throttle response... then I let it idle. it would bounce from 1700 rpm down to 800 rpm, and back up, and back down.. I thought it would fix itself, so I walked away and drank a few bottles of gatorade...went back to the garage and there was no change. The idle is still screwed up.
Sooo... I went back to the forums (searched on the G37 since there is a ton more info for the same damn motor) and then realized I shouldn't have been so aggressive cleaning the butterfly valve and the TB where the valve closes, but I should be able to do the idle re-learn and the throttle position relearn on/off tap dance with the gas pedal. I tried a dozen times and couldn't get any change....so, I called the fearless Stealership and asked how much they would charge to do these re-learning procedures for me...of course, they asked for the story and I told them what I had cleaned and they tried to tell me that I damaged my Throttle Bodies and I should come in and have them confirm that and replace them.
Sooo... I make an appointment for today.
Meanwhile, I start my car back up to move it back all the way into the garage and as soon as I put it in drive, the idle came down to normal...I put it in park, all still normal!
Took it for a drive and wow - what a HUGE difference in responsiveness and smooth idle. I drove it about 100 miles or so of city driving over the weekend and MPG was almost 21! (Normally, it would be about 19 when it was running good and before the G37S exhaust)

The moral to my story is be careful when cleaning those throttle bodies, don't move the valve if you can help it and don't wait till 88K between cleanings! Doing all of those things (filters, plugs, sensors, throttle bodies) sure makes a huge difference in responsiveness.

Nice to hear that the disaster was averted!

I like reading these stories about working on your car. We think we're prepared for the job, but then Murphy comes out and merely laughs at us as we struggle, get frustrated and worry. Looking at the bright side, there's something to be learned, even though sometimes it's at our expense.

Thanks for the tip!

I will say I'm glad to have a car I can do some basic work on again without the constant possibility of complete financial ruin should something go wrong, like I had on my Mercedes. I son love that we have a place to go talk about it. My wife tries to feign interest, she really does.

Planning to change the diff and transfer case fluids in the next month or two as well as the spark plugs, and extract the snapped off peg of the radio antenna and replacing the mast. Recently Plasti-dipped the roof rack cross bars due to scratching them getting the paddle boards on and off, as well as some rust starting to run off the screws in the tops of the bars.

Ok, so solved might have been a strong word. The startup and idle issues are still resolved, but the "stutter/stumble" when I let off the accelerater then get back on it lightly at perhaps 40 mph. Goes away after a couple miles.

Anyone have any thoughts? I know the plugs are due (at 97k and I'll eat my hat if they really last until 105k).

my plugs looked pretty crappy at 88K. It should help...can't hurt!

Geez - I have a new fuel pump sitting in the box in the garage with plans to replace this weekend. I guess I will look at throttle body too. I have same issues at 97k but I have already replaced plugs and installed new red silicone intake tubes from HPS.

Does anyone know where the fuel pump fuse is?? I got the illustration from the tech manual but I can't decipher the illustration. It is in the IPDM E/R where ever that is?? Checked the fuse holder in battery compartment & in the kick panel on driver side.

Thanks for any help guys>

mikey1951 wrote: ↑

Wed Jul 19, 2017 6:56 pm

It is in the IPDM E/R where ever that is??

IPDM E/R = fuse / relay box in engine room aka engine compartment

@mikey1951, with Nissan V6 engines I've learned they are crazy notorious for developing dirty MAF sensors and throttle bodies. Starting back with my 00 I30's VQ30DE-K, through my 07 G35 and now the EX, it's become increasingly clear that these engines are far more sensitive than most to changes within the intake system.

In short, no matter what the symptom anywhere on the car, check the intake system for crap.

schaffs04 wrote: ↑

Wed Jul 12, 2017 6:13 am

Ok, so solved might have been a strong word. The startup and idle issues are still resolved, but the "stutter/stumble" when I let off the accelerater then get back on it lightly at perhaps 40 mph. Goes away after a couple miles.

Anyone have any thoughts? I know the plugs are due (at 97k and I'll eat my hat if they really last until 105k).

This happens to mine too... has been like this for the past 2 years. Cleaning the throttle body & changing the spark plugs didn't do a thing. Did the 120K service, and nothing changed. The dealer said it's fine. Doesn't bother me really.

Found the fuse box next to battery - I decided to clean throttle bodies and I now have them both removed and on the bench ready for cleaning. I have TB cleaner and will be gentle in the cleaning. Also I have the neg terminal disconnected. They are both dirty as I expected.

Questions: Move the valve to clean edges of valve & seat?? Is there a relearn process??

Thanks guys.

JOB DONE!!! I did go to local Nissan for a little advice before touching the tbs - don't touch valve when tb removed. I cleaned the tbs as gently as I could and of course I could not get the edges. Reinstalled and it started right up with no issues - idles smooth as silk - ac on & off and rpms went up & down with zero issues.

Got on it on test drive and it doses have a more throaty engine roar. Smooth as silk but I will not be out of the woods till the wifey drives it this week - fingers crossed.

97k on the clock - plugs done last year & new hi perf silicone intake tubes so I should be good for a while.

I'll post if I encounter new problems.

well issue returned - cleaned maf again - I will call dealer techs tomorrow.

Let us know how it goes and what the next step is/was

Update: I was successful in relearning pedal,throttle close & idle air volume after reviewing my first few attempts (misread mil light on instructions) and it seems to be better. Today it stalled once out of 30-40 attempts under stop & go conditions. It failed when 1200-1500 rpms reached and then sudden release of pedal - rpm would fall to ~ 400 rpm or quit.
I personally tried ~ 20 slow starts & pedal release with no failures & one instance of drop to 400 rpm.
A gearhead friend suggested I remove electronic motor & sensor from TBs and clean the internal valve ( may be sticking) Nissan dealer does not sell sensors as a serviceable item.
Has anyone disassembled this unit to get at internals??
103k miles - new plugs & new siilcone intakes x 1 year. K&N filters x 1 year (cleaned & oiled x 3 months). TB were dirty - valve not moved. TBs totally removed for cleaning.
Upon start up I had no issues with idle or throttle response but the stall issues returned.
I am at the point of guarded success and will re-evaluate after a few more miles.
My next action would be to attack the tb motor/valve cleaning if the problem returns & persists.
Thanks guys for your info - waiting to hear from y'all!!

update part deaux!
I removed tb again on driver side and then unbolted tb motor assembly form tb. Internal unit is full of gears (3) and a rounded rectangle recess in plastic cover with metal sensors inside. I Manually turned gear to open throttle valve - did not remove any gears - and while valve was open I cleaned the edges of valve and the area where the edges seat. You will notice a set screw where a lever will butt up to when tb valve is closed. Don't touch.
I reassembled & installed - did the relearn without errors - test drive and did not even come close to stalling. Now the ultimate test by the wifey and I will do the passenger side when she returns.
Maybe I am near the end of this process.
TTYL8R

additional: don't remove gears - they will slide off axle - also the recess in the cover is where the tb valve axle end rests.
Progress is wonderful!

Oh yeah - you will need #20 torx/star socket with hollow end. In the torx screw there is a nipple in the center which prevents you from using a standard torx socket.

A final point: a Nissan/Infiniti stealership will sell you the entire throttle body while a good indy shop can give you advice on a complete cleaning by removing electronic fixture.
After cleaning edges and tb seat I could see a sliver of daylight around edges of tb valve when valve is closed but not touching set screw - I don't recall how it looked when I counter rotated gear to close and hit set screw.
I will update again after doing passenger side.

DONE!!

Finished passenger side earlier and all is well!! I observed the valve is not 100% closed in the throttle off position but you can rotate gear backward to mate up against set screw stop to have throttle valve 100% closed.

I can't think off anything else to offer except give yourself plenty of time and be patient.
Adieu!!!

Awesome persistence! Glad you got it completed. I know what a relief that is.

DAMN!!!

Stalled on the wife twice today!!!! CRAP!

No Codes recorded in memory - just P001 Fuel System Open : std code with ignition on???

I think I will visit the 350Z now!

OK - P0001 code is fuel system fuel pressure error. The fuel pressure regulator is a serviceable item attached to the fuel pump (in a box in my garage) so it looks like a new fuel pump install is in my future.

Having a vacation with the kids next week so it will a while before I tear into it.

Anybody here replaced a fuel pump - I know where it is and how to get it out but clueless beyond that,

Thanks guys.

It seems I need to check for fuel line leaks for pressure drops because the P0001 is a generic code which may lead to the pressure regulator in the end or may not.

I did find the fuel line to the TB was a little corroded at the metal nipple. I'll clean and do a full once over with all the lines

TTYL

Update: Reexamined fuel line connections to tb and found one not connected above flared area and another not pushed all the way up to tb. Reconnected all lines on both tbs and did a test drive x 2days with no failures. RPMs dropped from 1200-1500 down to 800 upon pedal release at low speed. Read for codes and no new ones - just the P001 stored in advanced dtc library. Erased library an d the P001 code did not return.
Sooo, maybe it is solved. Give it a few days and if I don't repost then consider problem solved. Yeah

fingers crossed!

Much better - stalled a couple of times last Wednesday but no issues since.
Now I have a coolant leak but not running hot - puts some stop leak in & so far maybe a capfull with slow drip x 4 days at front passenger side in front of condenser. Removed under panel and will watch carefully.
I watched you tube videos to replace radiator - tedious but cando!!