Hey guys. I have this issue where my 08 g37 seem to stutter and hang at 2k rpm. Usually when taking off in first gear there is a little pause at 2k rpm and then the rpms jump quickly and makes the launch uncomfortable. And when driving at whatever speed at 2100 rpm the car starts to shake and feel like it will die. I have attached a video of the issue while stst stationary as it was hard to get the issue on camera when driving. Engine light is from a broken o2 sensor (i have test pipes). Any help would be appreciated.
https://youtu.be/IRpEn0P80vg

 

Anyone? I still cant figure it out.

 

Seems like a tune issue. Contact your tuner or run the car on the performance map and see if that fixes anything.

 

Ive contacted my tuner and spent hours with him but he cant figure it out either. The problem was still there when he flashed the base tune. It kinda seems like its misfiring but only at that exact spot. Really frustrating

 

To me, that is an engine misfire at 2,000 RPM.

Use an OBD app (OBD Fusion works well) and view/datalog the live data of the short and long term fuel trims for bank 1 and bank 2 while having the engine at 2,000 RPM.
Your total fuel trim is the short term + the long term and they should be between -15 to +15 for each bank.

I have seen a few cases where the disconnected rear O2 sensors have caused fuelling issues.
Many think the rear O2 sensors don't have any input into the fuelling calculation, but other manufactures (Ford) use them to check for a lean or rich bias on the pre-cat air/fuel sensor.
I suspect Nissan/Infiniti does the same.

Anyways, knowing your fuel trims will tell you what is going on, and it also may be helpful info for your tuner.

 

I cant seem to get the obd fusion app to work. The only app thats working with my obdii scanner is the ndsiii on android.

 

Also i replaced the broken o2 sensor and the code went away. But a day later 2 more codes popped up. P0150 and p0051. These are also related to o2 sensors. This car has been a nightmare for me. Nothing is going right

 

The P0050 code indicates there is a problem with the front air/fuel sensor heater for bank 2 (driver's side)... this may be the reason for the P0150 code (ai/fuel signal is constantly out of range)
Check the wiring and use NDS to view the front air/fuel sensor's output. Here you can compare bank 1 to bank 2. NDS might have a PID to show the heater current, but I can't remember.

Don't be too hard on yourself... Sometimes when we mod a car, it can create problems that were not wanted or expected. Step back, take a breath and continue to work on the problem.

I have been helping G37 owners with technical issues for the last 5 years and it seems test pipes can be hit and miss to get the car to run without a check engine light or some weird fuelling issue.
Too bad you don't see posts like "I've had my test pipes in for a year and no CEL", then we could get a sense of how often issues really happen.

 

Thanks man i really appreciate the help. Is this the o2 sensor thats next to the headers? Could the o2 sensor on test pipe cause the upstream sensor to read bad? And could a broken or dirty maf sensor cause this?

Also reckon you could have a look at this logfile i recorded using NDSIII. Im not too good with the technical numbers and stuff haha. Thanks!
Datalog link: https://drive.google.com/file/d/1fjn...w?usp=drivesdk

 

You are welcome

Yes, the front or "pre-cat" or "sensor 1" is the sensor closest to the engine.

On the G37, it is not an O2 sensor, but an "air/fuel ratio" sensor, with a typical voltage output of around 2.2 volts when the air/fuel ratio is 1 lambda / 14.7 afr.
The rear or "post-cat" or "sensor 2" is the old style O2 sensor and will output about 0.9 volts when rich and about 0.1 volts when lean.

I will make a coffee and have a look at your log file.... back in a bit

 

In looking at the items you selected: RPM, Speed, Battery, Water Temp, Air Flow b1, Timing, Accel P1, TPS 1 b1, Injector b1, Power Str, Cls Throttle
Nothing odd stands out:


But there isn't any O2 sensor data in that log.

Try again and select something like Alpha (aka fuel trims), o2 sensor voltage, throttle position, MAF voltage for both banks, and anything that may indicate air/fuel ratio.

 

Oh thats interesting. Ill see if i can enable those data logging options in NDS. Ill get back to you very soon. Thanks!

 

OK so i selected a bunch of other stuff in NDSIII and data logged that. Hopefully its not too much data haha heres the link: https://drive.google.com/file/d/1gJa...w?usp=drivesdk

 

Too much data??? Never, the more the better...
Making a coffee and having a look shortly

 

Legend:
• Engine RPM
• AF Alpha Bank 1
• AF Alpha Bank 2
• WBSnsb1 (wide band / air fuel sensor voltage bank 1)
• WBSnsb2 (wide band / air fuel sensor voltage bank 2)

Here is what stands out to me:
• 3rd graph: AF Alpha2 (similar to fuel trim) is a flat line
It should look something like AF Alpha1 (graph 2) , which has good max/min value

• 5th graph: WBnsB2 (wide band voltage bank 2) is a flat line.
It should look something like WBnsB1 (graph 4), which has good max/min value

Everything else in the data log looks to be ok, including the MAF voltage, rear O2 sensor voltage, throttle position, intake cam timing, and ignition timing.

Looking at this live data, it makes sense that you have those engine codes, as they point to an issue with the bank 2 air/fuel sensor and/or wiring.
Basically, the ECU is not receiving the bank 2 air/fuel sensor's signal.