Car stats
03 5AT coupe, 187k miles
All fluids topped off
91octane Shell and Chevron gas
Ztube with K&N filter are only engine "mods"
Plugs are NGK LFR5AIX (iridiumIX) (plug were put in about a month back at 185k)

Issue is sporadic, can go several drive cycles without it happening or it will come and go during a drive cycle. Has been happening for about 2 weeks.

WOT the car will downshift if necessary, RPMS start rising and issue creeps up around 4kRPM. Car will feel like it has a hesitation that almost feels like a rev limiter/fuel cut from 4k on. Zero codes pop up and driving under 4k and non WOT is unaffected. Im going to go to town in a bit so I will try to get a video of it happening. Does it on warm and cold starts.

Things I have done -
carb cleaner checking for vac leaks - nothing
Gas with seafoam - no change
Reset procedures completed... all of them - no change

Any help would be greatly appreciated as its now driving me nuts.

EDIT - My video is post 7 and another gent with the issue has a good one of it at post 6

 

i would check the fuel pump and injectors maybe.

maybe cleaning your throttle body? umm kinda just guessing here. get a video of it and it will be easier to help you out. also try to get your codes read anyway. the ecu will store codes that have been tripped but are not active to set off the check engine light

 

You hit upon some good points that I have been thinking about a bit.

Injectors will need to wait till next week till I can pull them and do a clean and flow check at the shop. Fuel pump has been mulling around in the back of my brain but it isnt presenting the dead throttle I had when I replaced the one in my Sedan a while back, Who knows its not like it takes long to swap the pumps out to find out. stranger **** has happened.

I own a Matco MD70. ZEEEEERO codes not even temporary ones, probably should have mentioned that in the initial post for clarification. Gonna go for a drive later specifically to get video of it IF it will occur and to let the scanner record the live data so I can do a review of it.

Thanks for chiming in hurley

 

I'm very interested in what you find out, I have an identical issue.

First time it happened I was doing about 40mph, floored it, kicked down into 3rd and went straight into hesitation. I say hesitation but it was more like harsh jolting and I could only describe it like you have - fuel cut or like hitting redline, except you're only at 4/5k rpm. The jolting/jerking is exactly like hitting redline on the 2003/2004 G's.

I experienced it back a few times at WOT, kick down to 3rd, jerky revs at 4000rpm, let off and it goes away, back on the thottle and its jerky at 5000rpm and then I just take it easy. But yeah, it feels completely like hitting redline.

I do also have ABS/VDC/Slip lights on because I believe the used wheel bearing I installed wasn't working well with the ABS sensor. Other than that, the tire setup had me thinking. Are you running oem tyre diameter? Maybe the Trac control is kicking in?

This is on a ~100k mile engine I swapped in from a 350z

 

Hey Brad, sorry to hear you are also having this issue. Exactly what you have described is how I feel it is doing.

In my case I know its not the Trac control kicking in as the slip doesnt flash nor does the car try to compensate like the it does when it actually is kicking in. I have been running the current set of tyres for about 6 months with zero issues. Car is currently sitting on Achilles ATR sport 2's in 275/35/19 in the rear and ATR sport 245/40/19 in the front. Wheels are 370z Rays. I can only recommend in the case you are having getting a high quality scan tool that can read the various computers in the car and it will tell you what sensor in the ABS system is going out on you.

Funny thing, My Z33 had a front knuckle issue a while back and we just slapped one on from my parts G sedan, the ABS system light remains on as the sensor doesn't look to the right area as the location of the sensor is different on a G35X. No drivability issues and only a ABS light. I have just been too preoccupied to go get the correct knuckle.

 

I just went out this morning and took this video.
I was cruising around 70, then gave it WOT, kick down into 3rd (I think?) and goes straight to 5000rpm and you can see the revs bouncing like its at redline and you can hear. I think this is exactly what you're experiencing.
I also had experienced this at lower speeds/gears like I said in the other post.
Also after 90mph WOT doesn't pull like I'd expect either.

EDIT: If I floor it from standstill I can still hit red line as normal. But I consistently had this behavior at around 40/50 mph in I think 2nd gear and ~70mph in 3rd.

 

THAT is pretty much it. I am glad you got a good video of it as mine is just shoddy.

<iframe width="420" height="315" src="https://www.youtube.com/embed/-6R-BNxPzOQ" frameborder="0" allowfullscreen></iframe>

 

What mods or changes have you done that might have any effect?
I have
Test pipes
Exhaust
Larger tire size
And the car is 157K miles and engine is about 100K miles.

I've read problems with the fuel filter/pump normally just cause hard starts and unsteady idle but for 157K miles I wouldn't be surprised if it's contributing. I haven't driven enough with trac control on but how does it react to loss of traction? Does it fuel cut just like being at redline or shut the throttle a bit or?

 

***Possible Fix***

EDIT 1 - Assembly replaced on 5/16/16 with all reset procedured completed. Will report back findings on next drive.

So I think we pretty much nailed it down today at the shop. We hooked up the Modis scanner upto the car as it is able to directly read all the data from sensors ect. Parked and warm we tested everything and all looks good. No codes on any of the computer systems and all sensors have the correct data.

We take the car for a spin and low and behold it starts acting up. So on the graphs for accelerator control everything is out of wack. We tried it again for ***** and when it acted up we pushed the accelerator pedal to the right with our feet and low and behold the data corrected and the car took off like it normally would.

SO I got on the prodemand and looked up some data for the accelerator pedal position sensor and found a interesting notation about past fixes. I will post the printout below. But essentially this issue normally pops codes but I found this instance in the computer about where it was not throwing a code.

Im going to pull the pedal assembly out of my parts car and install it in the coupe and see if the problem is rectified.

 

So far so good. Been driving around running errands all afternoon. Time will tell if that was the issue or not.

 

I think you may have actually solved it......
Because I forgot to mention I had codes for throttle pedal something something I think it was P0123 and P0223 but I thought the fault had nothing to do with the pedal.

Let me know how that goes and I'll be grabbing a throttle pedal assembly from a parted out car.
I did notice today that sometimes I could easily get the car to do the hesitation then sometimes she was perfectly fine. I might try pushing the pedal left/right as well and see.

 

for the record, its held in by 2 10mm nuts and the wiring connector. took literally 5 minutes to walk to parts car, pull, walk across yard to the coupe and swap and pedal relearn. I will update as needed on my end Brad. If you have issues finding a pedal I know of 2 at nearby wreckers if you need one.