I get a stutter and a little bit of lag when I gently push the gas pedal (as in slow traffic). Smooth idle (albeit a little high since I just cleaned the TB's). If I do a pull with more than about 75% throttle I get a P0455 code (which also pops up a few days after filling up, but only about every 3 or 4 tanks, already replaced the gas cap). Any ideas besides a vacuum leak?

 

If you cleaned the throttle bodies, you may need to do an idle-relearn.
I'd clean the mass air flow sensors for starters on the hesitation.

 

P0455 is when the ECM recognizes the circuit to the EVAP purge solenoid has a dead short, it's usually the solenoid winding failing but it can also be damaged wiring or harness.

This has nothing to do with a vacuum leak, the ECM has recognized a faulty circuit, electrical problem.

I would remove the EVAP solenoid and bench test it to see if it's working at all. Typically they are just a 2 pin harness and receive battery voltage, supply 12v across the pins and it should open the valve, you can test by connecting a length of hose to one side of the valve, apply voltage, then blow through the hose. It should flow as freely as if the solenoid was not connected.

The idle stutter is a common side effect since the ECM is expecting more fuel vapor coming in from the EVAP canister and has trimmed back injector width to compensate but the extra fuel vapor never arrives because of a faulty EVAP solenoid.

Once the car tosses the code the engine probably runs fairly normal since the ECM stops trimming fuel because it recognizes the system is broken.

You still need to pedal dance the idle air relearn. Section EC - Engine Controls, page 18,19.

 

Got the pedal dance to work after a few more tries. Still haven't had the chance to test the purge valve, luckily it's easy to get to. I'm also thinking the stutter could be a misfire, but I haven't had any of those codes pop up. I have a new set of plugs for it, just need to get the right size socket.

 

Did u ever find the issue

 

nope, new plugs didn't change anything and the purge valve tested fine.

 

So, here we are, 2 years later, and I have a pretty good idea of the cause. I randomly put it in sport mode while driving around and noticed that there was no stutter at all. I'm going to test this theory out over the next few weeks to see if today was just a coincidence. What it leads me to believe is that I need a reflash of some sort. We shall see.

 

So did you ever find the issue?

 

I'm having the same issue with my 08 G35X as well... I'm changing spark plugs, cleaning maf and throttle bodies, intake plenum etc.. already replaced EVAP purge solenoid and idle relearns etc. but no success. I've heard about EVAP Canister Vent Control (Purge) Valve can maybe cause this issue but I havent replaced it yet..
Any luck with yours? I'm wanting an UpRev tune eventually as well so if a remap is the move (Like your Sport mode might be doing) then I'll feel better about that.

 

Disconnect the purge valve and the canister and blow air through the line to see if it's plugged up.

If your lines aren't plugged, you have a new EVAP solenoid, then it's probably either at the canister or the canister to tank vent lines.

There are other lines on the gas tank that are notorious for getting debris built up in them like the fill neck vent so it wouldn't surprise me if others like the EVAP canister to tank lines are crudded up as well. Wait until your gas tank is down below 1/2 tank (the emptier the better) and pop off the purge lines and blow air into everything to see if it's even flowing.

Make sure to open the gas cap anytime you're blowing air into the gas tank, otherwise it balloons up and when you take the air off it it's pushing a lot of vapor (and sometimes fluid) back out.

 

Late update. Stutter is still there, even in manual mode. I changed the purge valve on the canister a few weeks ago when I had her on the lift for new brakes and haven't had the P0455 come back at all, so that was the issue there. With talking to my dad he thought that maybe there was a trans fluid pressure issue at that particular engine speed. I basically disproved that when the wife and I went and drove to look at christmas lights. I had no issues letting it creep through the neighborhood at idle, and was even able to ease on the gas and accelerate until the engine reached about 1000-1100 RPM, and then it would trip over its shoe laces and stutter. Also noticed, while doing some spirited driving up the Coast Highway, that when transitioning from braking (be it engine brakes or the pedal) to power she'll make a clunk sound. But, only when the engine speed is in that 1000-1100 RPM range. Crawled underneath and looked at the engine and trans mounts and they look fine. The mystery continues.

 

Did it seem like the clunk was from the front or rear? Rear I would suspect the rear diff bushing, front would typically be a suspension issue rather than powertrain but I'd pull on everything under the car by hand to see if you can find some play. Also, on jackstands, with the engine off put the car in neutral and rotate the driveshafts, might be a lot of play in one of the differentials if the thrust washers are wearing out due to age or lack of maintenance.

To test the suspension I prefer the "rock the car" method, open your door, push up against the roof where the door jamb meets. Rock the car hard by hand to see if you can reproduce the clunk.

 

So, checked all my suspension bushings and engine/transmission mounts, all look good. Checked differential bushing, looked decent, but will probably replace soon, a long with ball joints. Rocked her side to side and bounced the front and back, no noticeable clunking. Then I got an idea, so I fired her up and went for a drive out to where I tested the wheel bearings a few years back. I tried the braking to power transition while turning to compare it while loading was on the right side vs the left. And guess what I discovered.....nothing. Then, when I got home, I tested another idea. I parked her, set the parking brake, put her in neutral and oh so carefully brought the RPM up, with no load. Sure enough, right around 1000 RPM the engine stuttered a bit and then was smooth again. Tried a second time and no stutter, but if I put her in gear and then back to neutral she would have the stutter, and only do it once. The mystery continues.

 

after more research I found this question and Answer from a "Jay" infiniti tech. The OP in the link was having similar issues as us but tried replacing camshaft retarders. idk about all that exactly but Jay's answer ultimately points to the dreaded gallery gasket inside the timing cover.

"What your issue is cause by is a blown back timing cover gasket. The oil pump sends oil pressure and oil operates the intake sprocket operation. Well the oil goes through this channel in the back timing cover. On the back timing cover there is a few gaskets along this ported area. When the gasket blows out, you get exhaust timing codes cause the intake timing operation does not get the proper oil pressure. To do this job, the front timing cover will need to be removed and timing chains to access the front timing cover. If you mechanic is not familiar with this issue, it probably best not to let him do the repair."

https://www.justanswer.com/nissan-in..._text=&irgwc=1

If you havent already, check oil pressure and check the oil pan for paper gasket bits.
Just before my 08G35x with 160kmiles got totalled, I pulled the oil pan for a new one and found paper gasket bits so maybe you could too. I never checked the oil pressure tho so thats as much as I can say on that. Good luck

 

Well, I can almost definitively rule that out, as this issue existed before I replaced the gaskets in 2021. So there's that. I haven't had any codes of any kind pop up since I replaced the evap vent solenoid back in March. While I haven't had the oil pressure checked, I'm not overly concerned with it.