Lean Bank2 SHRTFT 25% and P0300 random misfire at idle

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frankdrogotto
Posts: 10
Joined: Fri Jul 09, 2021 10:32 am
Car: 2004 Nissan Quest

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Help needed with 2004 SE Quest O2/fuel and emissions issue in Bank2 since mechanic replace my water pump; the symptoms are:

DTC code P0300 during idle only,
BANK 2 SHRTFT(%) = 25 steady at idle
The engine hesitates every 30 seconds exactly, when
----- upstream O2 sensor voltage rises to about 0.94v and
---- SHORT TERM FUEL TRIM SHRTFT(%) drops to 0


a- BANK2 emissions are abnormal. I need help to diagnose root cause:
O2/Fuel mix is lean and fuel trim is +25% steadily during idle..
Short term fuel trim drops gradually to around 11% during wide open throttle, then rises to 25% at idle.
---- Upstream O2 sensor voltage oscillates between 0.61v and 0.74v. (note this
---- SHORT TERM FUEL TRIM SHRTFT(%) = 25 (at idle)
Notes:
I created a vacuum leak on intake manifold to test, and did not observe impact on bank 2 readings.


b- BANK1 is confirmed normal:
---- Upstream O2 sensor voltage oscillates between 0.25v and 0.30v at idle
---- SHORT TERM FUEL TRIM % = low single digits
Notes:
I created a vacuum leak on the intake manifold, and it caused BANK1 fuel trim to increase to 25% at idle.
This and the derailed OBD readings, confirm to me that Bank 1 is good.
No effect on Bank 2 readings during this test.


Here's what I tried but no change in Bank 2 readings:
I replaced these parts:
- 6 spark plugs and 6 ignition coils
- 6 fuel injectors
- Bank 2 upstream O2 sensor (Reason: suspected Bank 2 upstream O2 is lying)
- PCV Valve
- MAF sensor
I added Seafoam to gas and oil .. been driving for 10 miles so far.

Questions:
Where is the most likely cause be since only BANK2 is behaving erratically?
Could Bank 2 Camshaft Position Sensor be going bad? (I ordered B1 and B2 CPS replacements)
Could Bank 2 exhaust manifold be leaking? (I don't have a smoke machine to test)
Could a leak further down the exhaust system induce this behavior?

Any guidance or suggestions would be super helpful.

thanks
Frank


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VStar650CL
Technical Expert
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Joined: Thu Nov 12, 2020 1:25 pm
Car: 2013 Nissan Altima 2.5 SL
2004 Nissan Altima 2.5 S

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It's pretty common for the bank2 chain to jump a tooth or two if a water pump replacement isn't done just right. When it's out more than 2 teeth you'll get a P0021 for the IVT control, but when it's only out 1 or 2 the symptoms are often just crappy performance. Get access to a scanner that can read your IVT angles, they should both be near-0 at idle. If bank2 is showing 3 or 6 degrees then a jumped chain on #2 intake cam is your culprit.

schuylkill
Posts: 167
Joined: Wed Jan 13, 2021 6:39 pm
Car: 2004 Nissan Quest SE

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I can't be more grateful that VStar650CL shares his extensive knowledge on a daily schedule on this site and I've learned to post my problems and get his insight before making purchases. When I replaced my water pump I indeed jumped the timing but my problem was on bank 1. Since I was replacing a broken chain guide I had the front cover removed and it was obvious there was a problem. Good luck on getting the issue resolved if it is the chain, I am curious how a shop would react if you used one.

frankdrogotto
Posts: 10
Joined: Fri Jul 09, 2021 10:32 am
Car: 2004 Nissan Quest

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schuylkill wrote:
Sat Jan 01, 2022 7:47 am
I can't be more grateful that VStar650CL shares his extensive knowledge on a daily schedule on this site and I've learned to post my problems and get his insight before making purchases. When I replaced my water pump I indeed jumped the timing but my problem was on bank 1. Since I was replacing a broken chain guide I had the front cover removed and it was obvious there was a problem. Good luck on getting the issue resolved if it is the chain, I am curious how a shop would react if you used one.
Thanks for sharing your case! I did use a local shop 3 months ago for this repair, and will take it back to them. The mechanic is experienced, and he opened the engine side to replace the water pump rather than do it through the inspection cover to ensure the chain does not skip.

What is the procedure for checking and validating a skipped tooth?
How much did you pay to get yours fixed?

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VStar650CL
Technical Expert
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Joined: Thu Nov 12, 2020 1:25 pm
Car: 2013 Nissan Altima 2.5 SL
2004 Nissan Altima 2.5 S

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frankdrogotto wrote:
Sat Jan 01, 2022 7:54 am
What is the procedure for checking and validating a skipped tooth?
Compression will be down a bit across the whole bank because of mis-timed valve openings, but there won't be other clues without dismantling stuff. As described above, the surest confirmation doesn't require anything but a scanner which can read IVT angles. You're not stuck with a Nissan Consult3+ for that, most high-end shop scanners can stream IVT readings.

schuylkill
Posts: 167
Joined: Wed Jan 13, 2021 6:39 pm
Car: 2004 Nissan Quest SE

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How much did you pay to get yours fixed?
Years off of my life! Since I had the front cover off (since the engine is rotated in front wheel drive vehicles the front faces the passenger side) I could visually see that the timing marks weren't lining up. I don't know if you should hope for that to be your problem or not. If the shop will fix it as their mistake I guess that would be a good outcome?

frankdrogotto
Posts: 10
Joined: Fri Jul 09, 2021 10:32 am
Car: 2004 Nissan Quest

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Eurica - A bad harness connector causing the Bank 2 Air/Fuel sensor to give illogical readings. This has been the culprit all along, I think, causing erratic O2 readings in Bank 2 and triggering pending P0300 and P0174 lean condition. Of course, this has been causing all sorts of hesitation, shaking, loss of power, and bad fuel economy. The bad connector caused the sensor voltage to flatline at 1.2v which falsely tells the PCM there's too much oxygen in the air/fuel mix; the PCM then adjusts short term fuel trim to the max +25%.

I discovered this when I fiddled with and cleaned the A/F sensor plug when the vehicle would not set the CAT and O2 tests to COMPLETE for Emissions Inspection. I used Autel OBD diagnostic tool and noticed that fiddling with the plug and harness the O2 sensor voltage changes from a steady flat 1.2V to normal around 0.58v and oscillating +/- as expected.

Any recommendation how to fix/rewire the connector?


Thanks!

macgiver
Posts: 1612
Joined: Wed Jul 04, 2007 10:21 am

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Did you try to spray-clean it with like De-oxit ? If connector is easy to get to you can treat it successfully until it totally craps out years later ?
Just too bad all those other parts were purchased and the labor to install :tisk:

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VStar650CL
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Joined: Thu Nov 12, 2020 1:25 pm
Car: 2013 Nissan Altima 2.5 SL
2004 Nissan Altima 2.5 S

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If it's the sensor connector or wiring that's damaged then there's no good fix. The sensor wires are stainless steel and not copper, so they won't take solder and crimp badly. Replacing the sensor is really all you can do. If the damage is in the harness connector or wiring, then it's perfectly okay to splice a repair.


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