Car randomly started limiting the rpm to about 5.5k after you drive it a while. Starting off it shifts perfect, but after a while it bounces pretty hard off that rpm range. Tranny is shifting fine, and it doesn't look like it's a fuel issue, as it pulls hard until then. I can downshift and hit past that range just fine, but as soon as you try and give it some throttle, it bounces/bucks. I can rev it fine over 5k in park. No CEL, no misfires, etc. Pretty stumped, as I have no idea on where to begin looking. Tried doing some searching but came out empty-handed. Car does have 240k+ on the clock, but I don't think it's mechanical, as it goes back to normal after you shut it off for a bit. Could it be TPS/throttle body related? CAM/Crank sensors? I'd expect it throw a CEL, tho. My other hunch is that it could be a fault in the ECU, but I have no way of checking what it's commanding when it hits that rpm range.
Any input is appreciated!

1-22-22 update: potentially resolved in post#30

 

I would start by pulling and inspecting the plugs to see what's going on in the combustion chamber.

 

all plugs and coils have been swapped last year (oem parts), so there is no (or very little) chance it's ignition related. like i said, it doesn't feel like a misfire.

i've pulled the crank pos sensor out and ohmed it out per fsm. 2 out of 3 connectors were in Mega Ohms (something like 30M) and the other was around 1.2k Ohms, so I have a new sensor on the way that should get here today. i'll ohm it out just to be sure, then swap it in. that's one messed up location for a crank sensor on these cars, i tell ya lol no idea how the ecu is not throwing the codes at me with these readings.

 

That's normal, it's a hall effect sensor. Basically you just don't want to see zero resistance, or an open circuit.

The only way to really check those things is with an oscilloscope so you can see what the ECM sees.

As for it being not related to ignition... you said it's bucking, that spark or fuel cutting out. You can see which one just by looking at the plugs usually, either it's running hot or it's running rich and it's going to show on the plug.

Check long term fuel trim, if it's really high you might have a clogged fuel strainer but I doubt that's the issue since it would immediately resolve itself when the rpm's came down rather than requiring a cool-down period. Possibly the O2 sensors are sending a bad signal due to clogging though and cool-down helps, again, reading the plugs will show things like this.

Doubt it's MAF, possibly throttle bodies, possibly CMP/CKP, possibly a bad ground somewhere that's actually causing an intermittent cut in the entire electrical.

Possibly the TCM pulling throttle due to something failing in the transmission.

Lots of various possibilities, I think going to Nissan for a 1 hour diagnostic if the plugs read good would be the cheapest option in the long run.

 

well, i'll be damned! apparently, my fancy tester took a crap on me. i got the new sensor in and it was testing the same as the old one... got a different multimeter i had laying around and the old sensor showing better resistance than the new one lol back to amazon it goes.

took the car out for a drive after properly warming it up, and it was acting even worse than before. i could push it past the 5k and beyond when revving it slowly, but if i hit the pedal hard, it would not go anywhere, like it was hitting a wall. parked it and after some revs it started blinking the cel at me (finally!). looks like i'm getting a p0304, so something to look forward to tomorrow... sure hope it's either a spark plug or a coil and not something more nefarious. way too early for either to give up the ghost, but stranger things happened before. i'll definitely not answer too definitely from now on (re: "there is no (or very little) chance it's ignition related" lol)

p.s. just thinking out loud. could it also be a plugged up cat?

 

I went ahead and tore into it today. Checked plug and coil on #4 (pics below). Nothing looked out of order (gap was good), so I put it together and drove again. It set a #6 misfire code, so I went in and swapped the 1/3/5 coils over to 2/4/6. It then threw a #4 misfire again. It never sets the codes on the dash, but just indicates that it's missing (i can then read the codes via the apps). I'm attaching some screenshots from the diagnostic apps below as well. NDSIII shows bank 1 wideband reading a lot leaner than bank 2 under load. However, torque is showing bank 2 sensor 2 oscillating like a standard nb upstream o2, which would indicate an issue with the cat on that bank (or an excess of oxygen?).

I'm at a loss right now. Plugs look good and i doubt it's the coils, since i've swapped the banks. Checked around for vacuum leaks and couldn't find anything. Probably need to test the compression to rule out the mechanical stuff.

Could a failing fuel pump be at play? Unfortunately, neither app allows to read fuel pressure.

A bad cat? I'm puzzled as to the lack of any codes, tho.

I'm also attaching a video showing what it's doing when i go wot at idle. If I ease into it, it lets me rev it higher, same on the street while driving it, but as soon as i hit the pedal to the floor it hits a wall.

Appreciate any pointers.




#4 plug

#4 plug

#6 plug

#6 plug

wideband bank1 goes a lot leaner than bank 2 under acceleration





Torque doesn't display correct voltage for the a/f sensors, but it looks like the rear o2 on bank 2 is oscillating while bank 1 is static. Does that indicate an issue with the cat?

 

In torque it's easier to go into graphing mode from the main screen, then pick the B1S1 and B2S1 O2 sensors, then just let it graph out (pretty the little play arrow button at the top) while you watch them both cycle up/down. I'm personally don't ever use that "realtime" mode that you are using. Always check O2 sensor cycling at idle.

It does look like something is up with bank 2 though, possibly the sensor or it might just be other cylinder conditions being so across the map that the ECM doesn't have time to make those minute fuel corrections that you will normally see the O2 sensor reading.

I would pull all of bank2 apart though, fully inspect the coil packs for blistering on the epoxy resin encapsulation top, scorching of the well tube boot, oil in the spark plug well tube, corrosion on the contact spring in the well tube boot, see if all 3 plugs look roughly the same with proper gap.

How long has it been doing this? Did it just suddenly start and do you think it could possibly be related to a bad tank of gas or has it been doing this for multiple fill-ups?

 

As for the video, with the car in park yes I'm pretty damned sure you will hit an rpm cut like that (maybe another V36 chassis automatic owner can chime in). Most automatic equipped cars will not allow you to redline in park and some even have a very LOW rev-limit in park, I think my Focus and Escape only go to 3500 in park.

If that's EXACTLY what your car does intermittently while driving you might have a PNP switch that's failing and intermittently wrongly telling the ECM that the transmission is in park while you're going down the road causing that 5k rpm cutoff. Next time it does that try to shift

 

thanks for the torque tip. i will do that as soon as i get my new obd2 adapter. mine took a **** on me the other day. i took the car to my mech and we had it hooked up to his scanner. added afr readings for both banks, mafs, tps, and timing. bank 1 was consistently going super lean at wot, and none of the other reading were suspect. we swapped the mafs around and still lean on bank 1. i took the upstream o2 out and swapped with a new one last night. old looked pretty bad. took her out and it was better at first, but then started doing the same ol' hesitation and falling on its face at around 6k rpm now. It "felt" a bit better, but it/'s obviously not it. I'll try to source an adapter this weekend and see what the O2s are doing.

regarding your second post. you might be onto something. i did replace my shifter console a few months back, when my manu-mode switch failed. i made sure the rod attached to the same exact spot as it was before. about a week or two ago, while going for a fill up, the car wouldn't shut off as it told me i wasn't in park, but i clearly was. i ran it thru the selector and it then shut off. i brushed it off as a fluke then.

 

Ahhh, yeah that's very likely the culprit then.

As for the OBD2 adapter, I've had excellent results with the BAFX Bluetooth OBD2 adapter with android phones, I have one of them in the console of all my vehicles in case I need to do a quick scan. Just be aware if you have multiple of the same adapter you will need to FORGET the Bluetooth adapter each time (from the phone Bluetooth settings), you can't just use the same settings for different adapters even though your phone will recognize it as the "same" device.

 

so i jacked it up and checked under for the lever engagement and everything looked good there. how would you diagnose a failing pnp switch? i assume it's the one the lever attaches to inside the trans.

also disconnected bank 1 upstream o2 to see if maybe the cat is the issue on that bank. at first it pulled hard, but once it got a little warmer, it started falling on its face in the upper rpm range. i'm hoping to borrow an obd2 adapter from a friend tonight/tomorrow and do some more data logging.

 

I have pretty limited RE5R05A experience but from what I remember and what I've seen in the FSM it a combination of both the gear selector in the cabin AND the TCM.

Gear selector is wired directly to the TCM harness, it tells the TCM which position the shifter is physically at, the TCM then makes it's gear selection based on this. The data is then transmitted via CANBUS to the ECM and the two talk back and forth for various other things (like not being in gear to hit an early rev limit).

Try to see if the dashboard is still displaying the correct gear while it's hitting that 5k rev limit in drive. Also try switching to manumatic mode to see if anything changes.

 

i drive it exclusively in the manu-matic mode (hence why the manu switch failed a few months back lol). I drove it just a few minutes ago, had to drop some parts at AZ. Small tangent: I normally tell them it's an '08 to not mess with engine types. Do not buy a 2008 oxygen sensor for 2007, totally different connectors. Glad they didn't give me crap on the return. Anyway, parked it at AZ and went inside and was out in less than 5. Got back on the street and was able to push it past that rpm range in 1st (manu mode). A few minutes later, wanted to see what it was doing in D, like you suggested. Floored it and it is just getting stuck around 4-5k rpm and not going anywhere, not even upshifting (it was still showing D on the dash). Just makes a buzzing noise and completely falls on its face. It's definitely related to the car cooling down and then heating back up. I can get over that hump if I don't floor it and ease into it. Same on idle in P. @WOT it gets stuck in that rpm range, but if i back off it and ease into it, rpm keep rising.

Thanks to the board for "related threads" feature, this thread looks almost like mine, and his issue was some relay in the TCM (but in his YouTube video he posted he tells someone it was a rip in the intake hose): 03 g35 full throttle issue in lower gears - G35Driver - Infiniti G35 & G37 Forum Discussion
and another one: Hesitation when accelerating in high rpm - G35Driver - Infiniti G35 & G37 Forum Discussion guy never resolved it. his was closer to my issue, as he was also stuck at whatever rpm @WOT. he was going to change out that acc pedal as his last resort.

i've read so many threads in the past week that my eyes are glazing over lol most (like 99%) have no resolution, so i'm hoping to figure this one out and actually record this on the internet lol

 

I really doubt the APP is the issue since you said it's basically hitting a redline limit, APP wouldn't do that.

Honestly I think your best course of action is a 1 hour diagnostic at Nissan/Infiniti.

As for the model year discrepancy, 2007 coupe uses the DE engine which has different sensors, always make sure it's a 2007 SEDAN with the HR engine they're pulling parts for. 2008 coupe is actually the G37 with the VHR engine so you can end up with VHR parts accidentally as well.

Nissan didn't do any favors by allowing the sedan/coupe transition to happen at different years. I run into the same problem with my 1999 GMC Sierra, it's a half-year, early 1999 was the early body style with the throttle body injected engine, mine is the later/newer body style with the LS1 engine...

 

yeah, i doubt it's the pedal also. i will go to the dealer if the next several things i test fail. i've ordered an exhaust back pressure tester from amazon that should be here tomorrow. the more i read and think about it, the more it looks like it's the cat(s). i do hear some rattle that's coming from the bottom of the car (driver side). i'll add several links below that sound like my issue. on one hand i hope it's the cats, on the other i've been reading how much of a pita those bolts that you can only get with like 10 ft of 1/2" extension are. i'll keep this updated.

closest one to my issue: Clogged Catalytic Converters and Symptoms Thereof | Pontiac G8 Forum (g8board.com)

one from these forums: Problem! - G35Driver - Infiniti G35 & G37 Forum Discussion

one from a bimmer forum: Can exhaust cause a lean code? | BimmerFest BMW Forum