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Discussion Starter · #1 ·
Long time listener first time caller 馃槀
Heres the scenario, i have an '07 2.5L 6spd with 267K on the clock. At 3K RPM i get something between a miss and a studder, to me it feels like a lean condition. It doesnt matter if im light or heavy on the throttle it does it either way. Ive tried a different set of plugs, i cleaned the MAF and cannot find any vaccum leaks. No other operating issues.

Heres the strange part, if i disconnect the battery for a few minutes the problem goes away for a couple of days (or possibly a certain # of key cycles) then it comes back. I do have a bluetooth adapter and the torque app but im not sure what i should be looking for. I still average 30 mpg so whatever it is the mileage doesnt seem to be effected just the performance.

Any suggestions would be greatly appreciated.

Justin
 

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Sounds like maybe a fuel trim issue. You should look at your LTFT (Long Term Fuel Trim) when it starts to act up. Disconnecting the battery clears out a lot of temporary data in the ECM and may be clearing your LTFT, which is a fuel adjustment gradually compiled as you drive. If it's moving way rich or way lean (+/- greater than 7~8%) then you may have a mis-calibrated MAF or bad A/F (front O2) sensor causing the ECM to mis-adjust its fuel map. The first thing I would try is an IAVL (Idle Air Volume Learn) to re-match your MAF to your ECM. MAF readings can change over time simply because the silicon components get old. What I usually do to determine if mis-calibration is the problem is take a baseline MAF reading at around 1500 RPM before doing the IAVL, then take another reading at the same RPM afterward. If you see a major change then the MAF was mis-calibrated. I've seen some drift as much as 30% on cars that went a long time from the factory without having an IAVL. For that reason, we perform it with every tuneup or fuel service at the shop. You should find an IAVL utility in Torque Pro's work support to DIY it.
 

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Discussion Starter · #3 ·
Thank you for you're very detailed reply. I will look at the live data then see if i can perform the IAVL. Im not sure if its a good thing or a bad thing but in the 155K miles (267K total) ive put on this car ive learned very little about it because nothing fails so only routine maintenance (oil changes, brakes, suspension, wheel bearings) gets done.
 

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Discussion Starter · #5 ·
Well i fired up the torque app and looked at the live data. Attached are two screenshots.

Driving 2nd Gear
Light Speedometer Gauge Tachometer Measuring instrument


Idiling
Speedometer Light Gauge Tachometer Measuring instrument


Looking through my torque app (android version) i dont see where i can perform the IAVL test, is there another way to do it? All of the "self tests" show green as passed.
 

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That negative LTFT is weird, the only thing that can usually cause that is the MAF or leaky injectors. So I think we're barking up the right tree. There is a manual procedure you can use to perform IAVL, but I forget the details. I work at a Nissan dealer and never use it since we use the Consult3+ scanner. I know there are other posts in here about doing it without a scanner, maybe Rogo or one of the other guys can point you to one.
 

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Here's a manual procedure for performing an IAVL:

Disconnect the negative battery terminal for 30 seconds to reset the onboard computer. Do not perform the relearn if the service engine soon light (CEL) is on and codes related to the mass airflow sensor, manifold absolute pressure, or incorrect idle speed are found. If everything is in order, we can begin.

First, bring the engine to normal operating temperature, 160-203掳F or 70-95掳C. Next turn off all accessories such as the air conditioning, rear window defogger, radio, and heater blower to prevent a load on the engine which would cause erroneous positioning of the throttle plate. Finally, make sure the front wheels of the vehicle are in the neutral position pointing straight ahead. We are now ready to perform the required relearn procedures:
----------------------------------------------------------------------------------

ACCELERATOR PEDAL RELEASED POSITION LEARNING

1. Make sure that accelerator pedal is fully released.
2. Turn ignition switch ON and wait at least 2 seconds.
3. Turn ignition switch OFF and wait at least 10 seconds.
4. Turn ignition switch ON and wait at least 2 seconds.
5. Turn ignition switch OFF and wait at least 10 seconds.

----------------------------------------------------------------------------------

THROTTLE VALVE CLOSED POSITION LEARNING

1. Make sure that accelerator pedal is fully released.
2. Turn ignition switch ON.
3. Turn ignition switch OFF and wait at least 10 seconds.
4. Make sure that throttle valve moves during above 10 seconds by confirming the operating sound.

-----------------------------------------------------------------------------------

IDLE AIR VOLUME LEARNING

CONDITIONS: Check Engine Light (CEL) with P0507 trouble code and high/pulsating idle, after disconnecting and reconnecting electrical to throttle position controller such as when cleaning throttle body.

Rectangle Font Parallel Pattern Slope


TOOLS NEEDED: stopwatch or timer showing seconds.

1. When engine COLD, first perform the Accelerator Released Position and then the Throttle Valve Closed Position procedure as shown above.
2. Warm up engine at this point. Drive on the road for not less than 10 minutes.
3. Car in Park, turn off all electrical powered stuff, wheels turned straight.
4. Turn key OFF and wait at least 10 seconds.
5. Turn key ON (not ignition) and start stopwatch at same time.
6. When stopwatch is at 3 seconds, press & release accelerator pedal 5 times hard and quickly within 5 seconds.
7. Wait 7 seconds or more and fully press the accelerator pedal and hold for approximately 20 seconds until the check engine light stops blinking and constantly stays on.
(note: If the CEL never starts blinking, then something is not working and you'd better start over again).
8. Within 3 seconds after the check engine light stays constantly on, release the accelerator pedal.
9. Immediately start the engine and let it idle. It may still likely be a high-rev/pulsating idle.
10. Let it run for about 20 seconds, then rev the engine a few times.
11. With foot on brake, shift into Drive. Idle should now go down under 1000 rpm. Shift to Park again, and the car should find its regular idle speed. Operation will be normal except CEL may still be on. It may disappear soon on its own, or you can do the following:

-----------------------------------------------------------------------------------

EASY RESET OF CHECK ENGINE LIGHT (CEL)

1. Turn key OFF and wait at least 10 seconds
2. Turn key ON (no ignition), wait 3 seconds, then press & release accelerator 5x hard and quickly.
3. Wait 10 seconds, then fully press accelerator.
4. After about 12 seconds CEL will go off then start blinking. As soon as it starts blinking, release the accelerator.
5. Wait 10 seconds, then fully press accelerator again.
6. Wait 10 seconds, then release the accelerator again.
7. Turn the key to off, then immediately start the engine. The CEL should be gone now.



Now, here's the big change

  1. Start engine and warm it up to normal operating temperature.
    AND RIDE YOUR CAR FOR AT LEAST 15 MINUTES, this will make for correct
    operating temperatures to happen within the engine for the following
    steps. Warming your car in the garage in the morning aparently does
    not cut it.



    Check that all items listed under the topic 鈥淧REPARATION鈥 (previously mentioned) are in good order.

  1. Turn ignition switch 鈥淥FF鈥 and wait at least 10 seconds.

  2. Confirm that accelerator pedal is fully released, turn ignition switch 鈥淥N鈥 and wait 3 seconds.

  3. Repeat the following procedure quickly five times within 5 seconds.

  4. Fully depress the accelerator pedal. Fully release the accelerator pedal.

  5. Wait 7 seconds

  6. Fully depress the accelerator pedal and keep it for approx. 20 seconds until the MIL stops blinking and turns ON.

  7. Fully release the accelerator pedal within 3 seconds after the MIL goes off. Start engine and let it idle. THE ENGINE MUST BE
    STARTED WITHIN THE 3 SECONDS AFTER IT STOPS BLINKING, THATS HOW THIS LIGHT GOES OFF. THE SERVICE MANUAL DOES NOT STATE THIS, BUT IF
    YOU LOOK AT THE DIAGRAM WHERE THE ENGINE LINE ON-OFF IS, IT CLEARLY SHOWS YOU SHOULD TURN IT ON
    WITHIN THESE THREE SECONDS.

This is where your engine will start to learn the correct idle settings

  1. Wait 20 seconds.

  2. Rev up the engine two or three times and make sure that idle speed and ignition timing are within the specifications.
 

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Discussion Starter · #8 ·
Well my findings are that the issue is still present and most noticeable in 3rd and 4th gears. Full disclosure i did not disconnect the negative cable (i didnt have time) before i started the accelerator pedal released learning so if thats necessary i will try the test again on Thursday or Friday.

I performed all of the tests after the car was up to operating temperature (40+ min of driving). Then drove for another 10+ minutes.
The LTFT is at least showing positive now. This was with the car stationary and the trans in neutral. SEL is not on and there are no stored codes.
Light Speedometer Gauge Tachometer Measuring instrument
 

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Discussion Starter · #9 ·
Update.
I still haven鈥檛 been able to track down the source of my 3K rpm stutter. Now that it鈥檚 getting cold outside the engine is acting up when I first start to drive. If the engine is really cold (like first thing in the morning) when I put it into gear and let the clutch out the car will sometimes buck and lurch for the first mile or two or until I鈥檓 above 1500 or 2K rpm with a steady load. Does anyone have any idea?
 

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I think at this point I'd suspect a bad MAF or a bad A/F sensor (front O2). The A/F should be reading around 2.2V when cruising with the car warmed up and the catalyst lit. It should spike way rich (low) when you gas it and rebound lean (high) when you dump the pedal, then steady again around 2.2V. If it seems to behave normally, I'd try a new MAF with a fresh IAVL.
 

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Discussion Starter · #11 ·
I will check the o2 reading today and let you know what i find. In the mean time is there a brand of sensors (o2 or MAF) that you reccomend or any brands to stay away from?
 

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I've heard a lot of complaints about aftermarket MAF's but in general I think they're unjustified, mostly it's people throwing a MAF at the car without performing an IAVL. The ECM can handle a wide latitude in sensor performance if it's properly calibrated. So you can go Auto Zone for that, just do it right. The A/F is a different story, Denso makes most of Nissan's units and I'd stick strictly with that or OEM. I've personally seen lots of problems with Bosches and even NGK's, not just China-cheap ones.
 

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I appreciate the honest opinion based on experience not just hear say.
You're most welcome, happy to help. We see two kinds of backyarders in this business. There's the sort that throws parts at the car until it won't even start and then tows it in cussing because it ain't like their '67 Oldsmobile, and we end up cussing and undoing half of what they did. We hate those people, no joke. Then there's the sort with a good scanner and a willingness to learn who thinks hard and asks for advice before throwing random parts around. No technician I know has the slightest problem with that. If the car eventually does come to us as a head-scratcher, we know we'll get a lucid explanation of the symptoms and a lot of good information about what can't be causing the issue. That's a joy and not a chore. :)
 

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Discussion Starter · #15 ·
Im a backyarder but with two associates degrees in automotive. The "part swapper" mentality is not part of my order of operations. My other 3 vehicles are Fords, which im very knowledgeable about but this Altima just hasnt needed anything other than routine maintenance in the last 6 years and 155K miles so i havent needed to learn much about it.
 

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Discussion Starter · #17 ·
Heres another one, this is a 4th gear WOT pull. I added a couple more signals just in case. When i let off of the throttle 1.0V is about the max that i see on the 02 sensor.
Speedometer Light Gauge Plant Tachometer
 

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That's very rich but not zero, which makes sense with your LTFT going very lean but no codes showing up. However, that doesn't exclude a MAF issue. If the MAF is under-indicating the incoming air then the ECM will be riching like crazy to try to compensate, but ping feedback from the lean condition will limit how far it can go. That will drive the A/F readings south and keep them there and also force the timing way retarded. I'd say check the ignition timing and see if it's either fluctuating or dialed way back when cruising. If so then suspect the MAF, if not then suspect the A/F.
 

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Keep in mind, too -- a lying MAF is the one sensor the ECM can't detect or properly compensate for. There's no MAP on a QR25 for the ECM to be able to cross-check. The ECM simply has to trust it, and that means when it's mis-indicating, the ECM will blame other things (if it even throws codes at all).
 
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