Hi all,

I've been having this issue over the last 6 months or so which I think has progressively gotten slightly worse.

When I go WOT the transmission will kick down (the videos show 5th to 3rd) and the revs will get thrown to around 4/5k rpm to match the wheel speed. Right at this point the engine will hesitate and the whole car jerks and the rpm's will continue to rise but in a slow and juddering manner (once you keep WOT). The first video shows me just going WOT and holding it, the second shows me coming on and off the throttle quickly to see if it will still create the jerky rpm - which it does. The feel can exactly be described as an "early rev limiter". Basically, I have hit the rev limiter up at 6500rpm before and it feels exactly the same except this is happening lower down.

To add to the explanation, this does not happen when accelerating from standstill. For example, if I floor it from a set of lights it will rev out the whole rev range, change gear, rev out and change etc with no problems whatsoever. The problem seems to be when the engine has to raise it's revs quickly. Again so if I was driving and manually shifted into 2nd or 3rd, raised the revs up to 4/5k calmly and then went WOT there is no problem. But if I were to shift into manual mode (instant 4th gear) and tip it into 3rd whilst mashing the throttle, it will hesitate like this.

Car details:
2004 G35 coupe
5AT transmission
Stock besides wheels, springs, test pipes and exhaust.

Video from 8 months ago - I've sorted out the sensors that brought all those lights on

Video from today


Any ideas on what to look at?

 

There was one single thread I found where the person was experiencing similar symptoms and the issue turned out to be the accelerator peddle....... seems far fetched but I might have to just find a pedal and see if it makes the difference. I was thinking along the lines of a bad fuel filter or weak fuel pump seeing as the issue occurs when the rpm lands right around the peak power range. Could bad spark plugs or dodgy coil packs do this? A scan revealed no codes for misfires and the engine idles pretty steady.

 

Bump!

I think it's getting progressively worse. Anyone with ideas on this random rolling 2-step

 

Check the diff bushing at the driveline connection in the rear of the car. If you see a black line going down your bushing has failed and your car will "clunk" at the driveline each time powers goes on or off.

 

Missed this post till now....
There's no clunk coming on/off power.
The problem here is when WOT (or like 3/4+ throttle now) after dropping a gear or two by automatic kickdown or manual gear selection the engine stutters and hesitates.

The videos show me cruising and then flooring it. The box drops into 3rd, the revs match and then the engine hesitates causing the jerky motion which feels exactly the same as if I were to hit redline.

 

Sounds almost exactly like when I activate rolling launch control (UpRev ARC feature). My hunch is that a sensor is failing causing fuel cut, but I don't know enough to tell you which sensor.

 

That's exactly the symptom.
I had the car scanned multiple times and never got anything in regards to a misfire code or anything hinting that direction. I have 1 code right now which is P0462 for the fuel sender unit. (Not sure about this, my fuel gauge reads alright I think but I don't run it down below 1/4 often enough to be sure - may not return to full every time after a fill up but the gauge works fairly accurately)

I did once have a code for the accelerator pedal, which is why I may just change it and eliminate that being a possibility. Even thought that code doesn't show up anymore.

Planning on changing spark plugs too during spring break as the ones in there are of unknown age/mileage - but still can't see this being the issue. Also will be pulling the filter in the tank to see if it's sludged up or something causing fuel starvation. But again, doubtful as it feels 100% like the ignition cut felt at redline/2-step/launch control.

If mechanical, I'm leaning towards possible fuel starvation.
If electronic, maybe a sensor playing up and "catching up too slow" when the engine rpms rapidly raise.

 

Any update ?

 

Haven't dug around with this as yet but I'm planning to do the spark plugs the week after next and check the filter in the tank. Also on the lookout for an acc pedal.

Currently chasing down an issue with bad tire wear which is taking priority.
A following friend said I shoot flames when it starts hesitating

Are you having similar issues?

 

Yes, And i replaced almost everything to fix it but no dice. oem 6 coil packs, new plugs, a set of low milage injectors, oem crank and cam sensors, even the valve covers since i had oil in the coil packs, re-man throttle body, swapped maf sensor, And the list goes on

 

Damn, so the issue you have is exactly like what I have in my videos in the OP?
Have you scanned for codes. What about replacing the acc pedal?

 

No CEL, No codes. Didn't swap the pedal though.

Also i remember reading on the370z forums about the brake light switch causing similar issues, Bought a new one and a new cruise control switch but no change !

 

Seeing as you've basically covered much of what I was planning to eliminate I think I will focus on getting an acc pedal. Only one other thread (350z or G35) where the guy was experiencing pretty much the same symptoms as me and after changing his pedal the issue went away. - I also had a code for the acc pedal but last time I scanned that code was gone so I sort of forgot about it till now.

Only other thing, have you checked up on the fuel filter/lines?
Is there a way to test the incoming pressure from the fuel pump?

 

My bad, I forgot to mention that I also replaced the fuel pump with a brand new OEM one from the dealer (the whole assembly) and no change whatsoever

The filter attached to the old pump looked fine though, I swapped it anyway since i didn't have a special adapter to test the fuel pressure.

Knock sensor & harness was also changed ! , Vacuum hoses !, 2 brand new OEM wideband sensors, 2 brand new oem o2 sensor (the one on the cat) and the list goes on !

Try a used pedal if you can source one for cheap or from a friend. Remove the negative battery terminal for a few minutes before you test drive.

Good luck.

 

That's exactly the plan.
You've pretty much exhausted most of the possible issues.

I'll probably source a pedal from a parting out car or swap with a friends and try.
Two 10mm bolts, one plug and neg terminal off.