Post by
frankdrogotto »
https://forums.nicoclub.com/frankdrogotto-u302403.html
Thu Dec 30, 2021 12:38 pm
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