Title really says it all.

When coming to a stop, or from standing start - if the vehicle is in gear, for example in Drive, and not moving (my foot on the brake), the RPMs stay around 500/600 RPM and the engine stumbles.

Put the car in Neutral or Park and it idles like a kitten. Put it back in gear - and it stumbles.

Give it gas in park or neutral and it revs fine, give it gas in drive or reverse and it drives fine with no hesitation or power loss.

This only seems to happen at Idle while in gear.

I've gone to a local performance shop that deals with VQ's a LOT and the guy suggested replacing my valve covers and plug seals. From there possibly the coils - after that he didn't know "until were at that point and doing compression checks on the heads"... which is all obviously time consuming and costly.

So - ideas as to what is wrong? Want to see a video?

 

Any CEL?

 

Did the problem start out of the blue or did it start after any maintenance was performed? It almost sounds like a small vacuum leak which becomes noticeable when the engine is put into gear and gets loaded up. Inspect your vacuum lines for deterioration, cracks and ensure they are all connected. Try and listen to for vacuum leaks.

 

To me it doesnt sound like engine issue. You say in neutral/park is fine.

Only drive at stop, maybe your torque converter or transmission. Because an engine issue would be less isolated, while transmission issue would be more isolated incidents. Its fine otherwise.

Maybe torque converter is locking more at idle than it should, maybe gears are gripping more at a stop than it should, putting more load on the engine than it should. Like a rookie driver ridding the clutch at stop light while braking, and bogging the engine a bit dropping the revs while not moving

 

Are you suggesting that the transmission be replaced or overhauled before the engine gets troubleshot for possible issues with the ignition, vacuum or fuel system? What troubleshooting recommendations or solutions do you offer for the problem you think Maybe happening?

I would troubleshoot the "Old School Way", I would do a good inspection of the vacuum hoses, ignition leads and electrical connectors for proper installation and security. If no obvious problems are found, I would probably replace the spark plugs first. I would definitely go for the low hanging fruit first, things with the least out of pocket expense. Just an old guy's opinion.

!Wow! I just noticed the numbers on my Points Bar "666 & 13", I'm playing lotto tonight.

 

Basic Detail Visual Inspection (DVI):

Ignition System:

Check coils for security, Leads for chaffing or cracking that could cause a High Voltage leak (HV leaks can be checked at night in the dark, sometimes a spark can be seen where there is an insulation breach). Here is a link to a type of tool that can be used to check HV leaks. http://www.dat-equipment.com.au/prod...kage-tester-2/

Vacuum System:

Check hoses for proper attachment, cracks and chaffed spots. Pay close attention where the hoses connect and check for split or stretched ends.

These suggestions costs you nothing other than time. During my first post I asked if the problem had just appeared or if it happened after some work was done. If it happened after work was performed, then something was disturbed to cause the problem.

Oh yeah! Here is a thought, in order to load the engine up some while in Park or Neutral, turn your A/C, High beams, flashers, wipers on and have someone lower and raise your windows while you check for the stumbling you mentioned. By doing this you will be putting an electrical/ mechanical load on the engine. This might help rule out the vehicle in gear question. (Trying to think outside the box).

Good Luck!

 

Here is one more thing for you to look at, now I am going fishing.

 

Okay, sorry for giving input. Merely suggested considering it was not engine. I didnt go and say go buy a new car or drop a new tranny. Geez louise. Take it down a notch

 

Sounds like you are having a bad day, you know with motorcycle issues and stuff.

Here is the thing, when you provide advise or suggestions, others might just listen and you don't want to mislead people and have them spending money on the wrong thing. Now I am not saying that the transmission idea is not valid, so your input is welcomed, I am saying that I would not go there without exhausting all other possibilities first. Lighten up brother! I just do this try and help with technical advise when I can.

 

It's all love guys - and another fine example of why G35 Driver is one of the very best resources of troubleshooting and technical support for the VQ.

I'm extremely pragmatic and methodical when it comes to this stuff - so all suggestions are taken in and considered... in the right order (low hanging fruit first as it were) of course

dEnbOy.GFM - as of that moment, there were no codes thrown. But in the recent past I'd been dealing with some CAM Position SEnsor codes (read below).

Wazz-upp - As for recent maintenance, yes there has been one thing done. In late June I began to get the P0340 code from Bank 1 (Passenger Side, the straight one) Cam Sensor going funny. I was experiencing stumbling under acceleration at speed (not at a stop), and both full engine shut off at speed (very dangerous) and at a stop. It's similar to what's happening now - but NOT the same. There is a difference in symptoms from then to what I've posted here.

So, I went off to infinitypartsusa dot com and bought the sensor. In August I installed it.

At that point within days I started to get P0345 Codes from Bank 2 Cam Position Sensor (Driver Side, the angled one) and had the engine shut off at speed and at stop continue to occur.

Then, the evening I posted this thread, after having driven the car hard (big pulls in 2nd, 3rd, and 4th all the way up to 6500RPM) I noticed after coming to a stop that the OP symptoms began. These newest symptoms had never happened before and I decided at that point to begin to look for input. And here we are... until today. Read next post:

 

All of the above said - This afternoon I went to replace the battery in the car with a duplicate from NAPA (75 Series / same part number as what's been in the car for 2.5 years) at the suggestion of the mechanic that is also suggesting the replacement of my valve covers and plug seals (there is some slow oil leakage around the valve cover edges along both banks)

I paid the replacement pro-rated charge for the new batter and upon installation in thier parking lot minutes later: the car would crank very fast, wildly almost (RPM needle jumping all over the place and indicator lights flashing all over the cluster randomly as if there was an electrical issue) and the smell of gas appeared... but no actual ignition, no matter how many times I tried as the gas smell got worse each attempt until I felt it best to stop (maybe 4 or 5 good long tries).

At this point I went inside the store and got my old battery back. I swapped my OLD battery back in - and the car fired right up first try. Ok, this is weird I think, so I swapped the new battery in again: starter whirls away with engine cranking to the moon (RPM and lights on the dash going bonkers like last time) and still no actual ignition. It was at this point I started getting a P0335 code.... So I swapped in the OLD battery again - and lo and behold...car fired right up!

Given what had just happened, I brought the first NEW battery back in the store and requested a 2nd new battery off the shelf assuming there must be something dodgy with the 1st new one (again all same models and brand) and plopped that (2nd new one) into the car. Guess what? NO START, SES and code thrown along with all the same symptoms as the previous two 1st new battery attempts.

So finally, I removed the 2nd new battery and swapped back in my current 2.5 year old battery and the car fired up first shot but with a bit of a stumbly rise in RPM... but it started.

After this whole escapade, and although I'm completely utterly confounded as to what the heck was going on with the car when either of the NEW batteries were inside it - I'm now getting a third code to worry about - the Crank Position sensor via the P0335.

Shortly after I got the second code (P0345) I ordered that second sensor, and it's in my center console waiting to be installed - likely I give that a shot tomorrow on my Sunday off and see where everything stands.

What a mess right?

 

I had a similar problem ,

I replaced the cam sensor bank 1 and all 6 coils with a used set of Low mile OEM nissan ones ,did a oil change .

And Car runs like a champ now.

 

I replaced the Bank 1 (the straight one / passenger side one) sensor a few months back based on the P0340 code the car was throwing out at the time... but it pretty much did nothing.

Now with the P0345 code (Bank 2 (the angled one / drivers side one) being thrown, I've bought that sensor (from infinity parts usa dot com) as well, but haven't installed it yet. In the meantime - as described above - I've started getting a P0335 Crank Position Sensor code. But Possibly I'll try new Coils as well at some point. If anything I wont write it off if everything else fails as it *is* a possibility

 

I'm back with an update.

****TLDR: Replaced all sensors, Now no codes but previous stumbling while in D at a stop persists. PLUS, now car bogs hard and looses power when trying to accelerate quickly by using WOT from any speed or from a dead stop.. But when using light gradual pedal / acceleration engine performs smoothly.

----------------------

I've now replaced all three sensors, the two (bank 1 & 2) camshaft sensors, and the crankshaft sensor. All are OEM parts bought from Infiniti parts usa .com. That's $336 in just sensors thus far (and all of my time of course - which as anyone knows, your time is worth money too)

So, new sensors, and there are no more codes now, but the stumbling in D while at a stop remains.... and there's something new, MUCH worse than before.

Now there is MASSIVE bogging while accelerating under WOT. Previously if I gave the car heavy gas it would accelerate rapidly but with some random misses and stumbling (that was before sensor(s) replacement) as it tried to get up the rpm range and increase in speed. Now, if I give it a lot of gas it just seems to hang, or something, and brrdddddddddddddddddd is the best description of the sound I can give.

Imagine a steady rpm and speed increase to be this:
123456777777 (where the 7 thousands are top of the rev limit in my 5AT's case)

From a stop, If I push the gas hard now, my car instead goes:
12333333333333

But f I push the gas lightly from a stop and then stay in the lower rpm ranges, my car goes:
1234... (in other words, light driving around town or even at highway cruising speed.. everything feels fine)

What's more, if I instead accelerate at a casual rate the engine does not stumble or bog, speed and RPM increase smoothly (albeit slowly as it you'd expect being light on the gas) and there is no bogging. But driven in highway traffic with the need for overtaking, you're mixing casual gas pedal pressure for maintaining speed with bursts of WOT for overtaking... well, here's what my car does in that instance now:

(Let's say highway cruising rpm is 3k)
333333333333(here I apply wot to begin lane change and overtake)45555555555555

When what should have happened when the car is working normal is:
333333333333456777777777


Any thoughts?

I had some, so here's what I've checked so far: Plugs & Coils. Plugs look "ok" and none had oil on the porcelain side (although most seemed to be gas/oiled up on the thread side.... then again my Stillen box runs a super rich rich so that's not very surprising. The coils also looked fine with no bubbling or mishapenness (sic) in their housings.... so I proceeded to do a resistance check every one of them and these are the numbers I got:

(I don't know what these numbers mean mind you)
Drivers side cylinders - Front / Middle / Rear (firewall)

As you can see I took reading of all pin combinations using both polarities. First the three going Red )positive) to black (negative) and then in reverse - as each polarity gives you different results, shown in the charts I made.

Passengers side cylinders - Front / Middle / Rear (firewall)


I also noticed that when looking inside the plug ends of the coils themselves, printed in the plastic by the three pins were two numbers. I took down what those numbers were for each coil and placed them above the charts for each. I have NO idea what those numbers mean... but since they were different from coil to coil I took note of them.

And here are a few extra pics of related things:
----

The numbers inside the coils I mentioned:


The condition of the plugs on the drivers side:


The type of plug I use because I'm supercharged (one step colder), and roughly the overall condition of what each one looked like when inspected:
***NOTE - I did find one plug on the passenger side whose electrode wasn't as pointy as the rest - but it wasn't completely flat either.. it was just not as pointy as the other 5.


The multi-meter I used to take my readings (with the plugs in the holes I used for those reading - ie, not in the DC 10amp mode)

 

Subscibing for curiousity.

Are there any electrical mods done to the car at all?