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Hello from Las Vegas

Helping a friend with a 2013 Pathfinder 3.5 that simply cannot make any power in gear. Holding pedal to the floor it would be a stretch to make 20 MPH. At idle in park it surges a lot but doesn't stall. Scanned for codes and found P0300 for random misfire and P0101 for MAF sensor/circuit. Owner claims the sensor is new. If in park and idling the MAF is disconnected, the idle smooths out and no more surging. That leads me to believe the circuit is intact. Also, if I clear the code with scanner at idle in park, it smooths out with MAF sensor connected. It will stay smooth until put into gear and a load on engine. As I mentioned above. WOT throttle yields almost a total cutoff from engine, however if I lightly apply throttle, I can accelerate more. But to be clear, partial throttle request still has reduced engine output. As far as the misfire goes, I cannot feel/hear/experience it at all. When in neutral, the engine will tach up. I am not a Nissan guy so cannot attest to whether it tachs up normally or seems to be reduced power as well. I don't feel this is transmission related even though neutral seems to produce more RPM, as it still surges in neutral or park at idle. Seems to be "load" related.

I rebuild GM 2.4 direct injection engines here in Las Vegas so I am not afraid to repair this vehicle, but was hoping for some hints on how to proceed. My scanner is a Bosch tablet that is fully updated and can program, however the Nissan computer has several different "routes" to info vs the GM libraries I am used to. For example I have not found the data stream that looks at a misfire graph by cylinder. I was hoping to take that random misfire code and narrow it down. Anyway any advice is helpful. Or ideas on where to diagnose next or what other info you Nissan peeps need to assist me.

2013 Pathfinder S
84,500 miles on odometer, owner says engine was replaced couple years ago. Above issue is a new development.
 

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Discussion Starter #2
Also, I forgot to mention I have a traction control light on as well as an ABS code of C1130-00.
 

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Don't sweat the C1130, that's a derivative code, just the ABS saying it can't hear an engine speed signal from the ECM. The behavior you're describing sounds like the ECM is going "limp", which puts the CVT in something approximating 3rd gear and limits throttle opening to something like 5%. If the new MAF is aftermarket then my first inclination would be suspect that. P0101 is a "performance" code and not "flatline", so you can try locating the Idle Air Volume Learn (IAVL) procedure in your Bosch's work support and see if the ECM will take it. It's possible the new MAF's readings are simply way off from what the ECM has in memory.
 

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Thanks. Let's assume that I cannot access the relearn process, what then? Is there a way to bypass that or is off to Nissan?
 

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In the GM vehicle I work on, the idle air circuit is bypassed at any value above idle. Are you saying that isn't the case here and could be the cause even at full throttle?
 

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I think it's off to Nissan. Yah, the MAF on Nissans is proportionally calculated, so the readings the ECM gets at idle affect the whole range.
 

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Anyway this theory can be tested? Would disconnecting the IAC change performance? Or possibly go to a "default" value?
 

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You could stream the MAF and see if it's putting out sensible flow figures. Usually they output a bit more than 1 gps per liter at idle, if it's way out in left field then it's probably your culprit. I should also tell you we see lots of issues with aftermarket MAF's, so it wouldn't surprise me if you discover it's plain bad-out-of-the-box and not just mis-educated.
 

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I was able to perform the idle air flow relearn procedure. No change.

Also spent time learning how to access the ECM with my scanner and found the misfire graphics. No misfires are stored in the memory nor are any occurring during the poor running condition.

The condition seems not to exist at a cold start up. By that I mean, it will idle perfectly until coolant temp reaches about 170° or unless load placed on engine (into gear). I assume it's in a "closed loop" setting by ECM and when criteria is met it switches to open loop and looses control and the condition occurs.

It honestly feels like it fuel related. I cannot find a port to watch fuel pressure, nor do I see a value in my scanner. Anyone know where the fuel port is located?

Any other ideas are welcome.

BTW, I didn't forget to test MAF readings and post here. I just didn't have ability to back prove sensor when I went over to the garage it is in. I will try today
 

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There's no fuel port, you need to break the connector at the rail and install a tee. If it's only messing up when it goes closed loop, fuel pressure is a good possibility. In open loop Nissans fire all the injectors at once, so volume means more than pressure. Once it's in closed loop the pressure becomes much more meaningful.
 

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No fuel port? Thanks Nissan. Any clue what size the line is at the rail so I know what size T to get?
 

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I have spoken to the owner again to clarify some points that I was unaware of and wish to update this forum's members in my plight for help.

Engine has NOT run correctly since it was replaced. The shop that did the work is completely out of the picture now and is not a source for possible clues.

Pathfinder is a 2WD vehicle, however the donor vehicle was 4WD. I have no idea if that means is equipped with different sensors or calibrated differently or???

Some GM vehicles that I am used to working with require the crankshaft position sensor to be relearned when it or the actual crankshaft (or complete engine) have been replaced. However that is an obvious code that ECM reveals when needed.

This ECM is very secretive and that coupled with my ignorance is making this mystery hard for you fellow board members to help.

I think I am left with towing it to dealership and paying for an hour of diagnostics unless there is something else you all can offer.

Thanks again for the help and time to look at my issue.

Also, if would help I can paste the complete diagnostics that my scanner provided during the issue occurring.
 

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Hooboy. Could be the ECM needs different firmware. Does the owner know if the donor was the same MY, at least? If he can give you a VIN for the donor, I can run the two numbers and see what systems might not match.
 

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The owner contacted the supplier of the engine and they are not providing the VIN of the donor vehicle. The only info we have is the receipt stating it was from a V6 4WD.

I feel that if it was fuel related I would be able to track misfires on the scanner both in stored history and in real time as it occurs. Also the engine that was removed ran well other than the smoking exhaust (Nissan claimed it was rings). So I assume fuel pump is good. I feel like the issue is a non-compatible sensor attached on donor engine or simply not connected (but would assume a MIL would set) or possibly a missed or damaged signal or ground wire. However I cannot see anything out of place so am leaning toward a sensor or its calibration.


A search on a few engine provider sites shows me that the 2WD and 4WD are seemingly interchangeable but perhaps I'm mistaken. Anyone know of a year break where there were subtle changes to the power plant? Maybe I can replace whatever changed and get the ECM back in control again.

I really feel like the ECM is getting bad intel from a sensor(s) and is not able to operate properly, but I don't know where to look.

I am not against the dealership for an hour of diagnostic if that is what is needed, but I don't want to drag it there and then get the call saying needs couple more hours and more etc all because the engine shouldn't be in there to start with.

I'm in 2 minds. The tech side of my mind says give Nissan service all known info on history to aid the recovery of culprit. The other side says take in and play ignorant on all matters on car/engines just to see how they carry on.

As of now my plan is Nissan on Monday morning unless anybody here has a plan of attack that I may try.
 

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I'm in 2 minds. The tech side of my mind says give Nissan service all known info on history to aid the recovery of culprit. The other side says take in and play ignorant on all matters on car/engines just to see how they carry on.
If you play dumb you'll simply send the techs chasing their tails looking for normal malfunctions, not mismatched parts or firmware. IMO you need to give them every scrap of info, and give it to the tech, not the SA. In a perfect world SA's would be skilled translators between mechanic-ese and customer-ese, but in the real world most of them don't know jack about what happens in the shop and will not pass on all your info. The tech will get whatever info fits conveniently on the front of the ticket and you'll get bad results.
 

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I was able to perform the idle air flow relearn procedure. No change.

Also spent time learning how to access the ECM with my scanner and found the misfire graphics. No misfires are stored in the memory nor are any occurring during the poor running condition.

The condition seems not to exist at a cold start up. By that I mean, it will idle perfectly until coolant temp reaches about 170° or unless load placed on engine (into gear). I assume it's in a "closed loop" setting by ECM and when criteria is met it switches to open loop and looses control and the condition occurs.

It honestly feels like it fuel related. I cannot find a port to watch fuel pressure, nor do I see a value in my scanner. Anyone know where the fuel port is located?

Any other ideas are welcome.

BTW, I didn't forget to test MAF readings and post here. I just didn't have ability to back prove sensor when I went over to the garage it is in. I will try today
The P0101 code being a malfunction with the MAF or it's related circuitry makes the ECU put the system into 'fail-safe' mode; engine speed will not rise more than 2,400 rpm due to the fuel cut. This condition can cause the idle to be erratic. It also can cause the re-learn procedure you performed to be non-effective. When you disconnect the MAF and find that the idle smooths out and no more surging is due to the ECU using a default stored fuel map in order to allow you to still operate the vehicle at much lower speeds. When you fix the P0101 problem, there's a good chance the P0300 problem will probably go away.

Your post indicated the MAF was replaced; what was the reason for replacement? Many of our members here on the forum have run into similar problems such as you encountered. They replaced the MAF with an aftermarket unit and experienced symptoms similar to yours. When replacing sensors, always use Nissan OEM parts from a Nissan dealer; aftermarket electronic components generally are not reliable, don't last long, and many times are DOA. Before you condemn the MAF, go through the tests indicated previously on this thread. If you don't have a copy of the FSM for your vehicle, you can download one from: Nissan Pathfinder Service Repair Manuals

Here are some possible causes for your problem:
• Bad harness or connectors. The sensor circuit may be open or shorted.
• Intake system vacuum leaks. To check the intake system for a vacuum leak, attach a vacuum gauge to a full vacuum source. With the engine fully warmed up, the reading at idle should be 18 - 20 InHg. At 2,000 RPM, it should be around 21 InHg. If readings are under 18 InHg, check the intake manifold nuts to make sure they are tight. The gasket may have failed; spray a water mist at the gasket to see if the gauge reading changes. Also check the intake plenum bellows at the throttle valve and at the MAF for cracks or loose clamps.
• Bad MAF sensor.
• Bad Intake air temperature sensor.
 

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The P0101 code being a malfunction with the MAF or it's related circuitry makes the ECU put the system into 'fail-safe' mode; engine speed will not rise more than 2,400 rpm due to the fuel cut. This condition can cause the idle to be erratic.
Maybe the earliest R52's are different (I don't have ASIST in front of me), but in most cases P0101 by itself will only put the ECM in a "limited performance" mode, not full failsafe. There are a number of TSB's about it on the Altima and others that begin, "MIL lit with P0101 and no driveability issues". Many times people don't notice anything but the MIL.
 

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Maybe the earliest R52's are different (I don't have ASIST in front of me), but in most cases P0101 by itself will only put the ECM in a "limited performance" mode, not full failsafe. There are a number of TSB's about it on the Altima and others that begin, "MIL lit with P0101 and no driveability issues". Many times people don't notice anything but the MIL.
Hmm. Interesting; the FSM only seems to discuss failsafe. However I generally don't look at TSB's unless there's some un-explained gremlin.
 
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