2014 Nissan Rogue P0300 - stumped

D60

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2014 Rogue Select (=old body style apparently) with 2.5L, 134k miles

Vehicle stalled at a stop the other day. According to owner it "revved" then sputtered and died. Vehicle would ALWAYS restart but stall within seconds.

In the course of troubleshooting I found if I kept it 2-3k rpm it would stay running. After enough of this it seemingly relearned fuel and/or throttle trims enough to run on its own.

Right now STFT is pegged (apparently) at +25. So, it's obviously adding a ton of fuel. When it's doing this it runs fairly well, but you can still hear a hiccup at tailpipe. Periodically it'll pull STFT to 0 and then stumbles badly, eventually returning STFT to +25.

Day 1 of test driving STFT was essentially binary: either 0 or 25. Even when driving under light acceleration or coasting it'd be 25, periodically trying 0 again (you could tell, too). Under heavier acceleration it would sometimes use a trim between 0 and 25.

Day 2 of test driving overall driveability was the same but it started to ALWAYS run STFT at 0 when off the accelerator, and 25 the second you touched the accelerator at all. Coming to a stop at idle returning to 25. THEN for a brief while STFT numbers started to look more normal while driving, running throughout the range and corresponding to demand. Coming to a stop returned to +25

CODES: I'm only getting a P0300 in stored or pending. ONCE I got a P0302 so I swapped the coil from 2 to 1, but have been unable to get another individual cylinder code.

PLUGS: they're Autolites so replaced at some point. They don't look stellar but I feel like throwing 4 plugs at it right now is an act of desperation.

VACCUM LEAKS: was unable to find anything with my smoke machine.

VVT SOLENOIDS: this would be nice but I'd sure love to see a code for one and I'm not getting any.

THROTTLE BODY: from what I can see looks relatively clean. Butterfly seems to move freely

ENGINE OIL LEVEL: full and appears clean

Basically, lacking codes for an individual cylinder, electronic throttle, VVT solenoids, MAF or O2 sensor (the latter I believe being irrelevant as symptoms are present even when stone cold), I'm unwilling to just throw parts at it.

I'm seriously beginning to ponder jumped timing which is apparently not unheard of on the 2.5. Presently I'm lacking a scope so I'm inclined to kick it down the road for a second (better) opinion but wanted to run it by BITOG first.
 
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If it’s out of time you should be able to hear it when cranking. It will sound “off”. With adding so much fuel, have you checked for fuel pressure/delivery issues? What exactly are the fuel trims going down the road?

What are your MAF readings/02 readings at idle ?
 

D60

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If it’s out of time you should be able to hear it when cranking. It will sound “off”. With adding so much fuel, have you checked for fuel pressure/delivery issues? What exactly are the fuel trims going down the road?

What are your MAF readings/02 readings at idle ?
It starts up quite readily now but I could disable fuel pump or coils to be able to listen to prolonged cranking I suppose

Apparently these don't provide a FPR reading but the pump primes to ~32 on the first power up and 50 on the second. I don't have a way to T into the line at the moment. My Autel MD808 doesn't appear to offer any live data that resembles fuel pressure and vids I've watched seem to involve shooting [whatever] into plenum to check for lack of fuel delivery.

STFT going down the road is typically pegged at 25. Sometimes it's 0 off the accelerator, 25 on the accelerator. For the brief time it started to at least do something -- ANYTHING -- else it was roughly 5 to 18 IIRC. I was hoping maybe a sticky VVT solenoid had freed up but the problem was still present once I came to idle
 

D60

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Oops...at idle MAF is reading .01 lbs

02 switching- if you graph it - looks horrendous, running 2.6 to 3.5V but I was ASSuming this was more a symptom than the cause.
 
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Did all four spark plugs look the same? i'd be curious about fuel pressure. I wonder what stft's would be if one injector was not working.
 
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I had a '14 Quashqai. Good vehicle. Those airboxes are always serviced and put back together wrong. Most confusing AF I have ever seen.

I would give the MAF a clean with CRC. Mine was filthy from the factory as the OE supplier over oiled the AF - it was dripping oil. And no the oil didnt come from PCV. This really sound like a cracked or leaking intake if FP is good. Is MAP in range at idle? Any one plug white? The QR25 has been know to fall apart the timing components - but cam position should be reporting that.
 

D60

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OMFNG it's the FN bugs!!!

Holy chizzynit, I've NEVER experienced something as stupid as this (either myself or what happened, take your pick).

First, thanks to @ARCOgraphite for the suggestion. I'm ashamed to say I never actually pulled the MAF sensor. Given the lack of codes and the fact that the tb appeared relatively clean I figured the odds of MAF contamination were exceedingly low.

WRONG! I love my bug zapper in the Colo summers but using an MAF sensor as a bug zapper just don't work out well! I attempted to capture ....behind the orange diode??......but my camera phone can only do so much.

THE SECOND I started it up the vehicle was performing VERY differently....holding a steady idle at almost 2k and fuel trims in the negative teens. Finally settled to basically 0 STFT and idle in the 750's.

SUCCESSFUL test drive. DONE

Thank you to all who replied
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Wow the famous bug messing up the works. He must have been the incorrect impedance.
That may be the gross IA temp sense component.

I really blame OBDII reporting for not being more rigorous. Seen many vehicles barely running with no MIL lit.
It's a joke actually.

I hope you got that airbox together tight I had to buy a "cheap" low tier STP air filter to get good engine performance.
The "High effeciency premium units weren't flooring enough air !
 

D60

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Wow the famous bug messing up the works. He must have been the incorrect impedance.
That may be the gross IA temp sense component.

I really blame OBDII reporting for not being more rigorous. Seen many vehicles barely running with no MIL lit.
It's a joke actually.

I hope you got that airbox together tight I had to buy a "cheap" low tier STP air filter to get good engine performance.
The "High effeciency premium units weren't flooring enough air !
Good to know on the filter. It looked like there was a basic Fram in there. I remember even before I found this I thought the "wedge block" style of air filter retention was kinda weird

I agree on codes.....I feel like the P0300 is just the catch-all.....like going to the doctor and only saying, "I don't feel well." Uhhhmmm, ok, can you be more specific? :D
 

D60

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Follow-up:

Ironically, this happened to the vehicle owner AGAIN several weeks later. She called me claiming identical symptoms, and I told her it was probably something else this time because the odds of fried bug TWICE in such a short time were incredibly slim.

She had it towed to a local shop whom I think is lackluster at best. THIS TIME they had an MAF code and she of course told them of the previous experience. I was kind of disappointed they had a lead because I wonder if this particular shop EVER would have found the problem with only a P0300.

The owner asked what else could be done to prevent this, I told her maybe a cheap STP filter as mentioned in this thread might seal better. I'm also not opposed to a screen or perforated sheet somewhere in the intake before the MAF, but I'd want to be sure it wouldn't restrict airflow too much.

I could SWEAR I've seen other OEM's place a perforated screen before the MAF. Am I delusional? (in the metal world perforated sheet is just sheetmetal with lots of round holes punched in it)

Whatever is used doesn't need to stop gnats but more like house flies and bees
 
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Like I said I have seen no one put the airbox together correctly. Not even the dealer Master techs. Not even me a few times - and I was paying attention!
I ran the base STP to get good airflow, there seems to be a spate of AF with poor airflow. Ran in to problems on our Subaru airbox.
Once got a Fram air fiter with the frame so warped the airbox wouldnt close. Those have a rigid-frame filter.

The car may have a bad MAF. Too many bugs. I would guess the car uses a wideband lambda. those are not switching - they read a sliding scale required for multifuel and better control. Not sure if the '14 QR25DE had this yet. That puppy likely needs a new Lambda by now, either way.
For shade tree diagnostic I drive it with the MAF unplugged and see if it will drive well at barely cracked throttle running on the lambda only running a stoich mixture.
 
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