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Fuel Trim Analysis, Nissan Pathfinder VQ40DE

Home Forums Stay Dirty Lounge Service and Repair Questions Answered Here Fuel Trim Analysis, Nissan Pathfinder VQ40DE

This topic contains 0 replies, has 1 voice, and was last updated by Brent Brent 3 months, 4 weeks ago.

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    Brent
    Brent
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    -2006 Nissan Pathfinder LE 4.0 V6 287,000miles (new to me within a couple months)

    -Valve Covers, pcv valve and associated gaskets recently replaced (oil leak) along with spark plugs (while I’m in there), crankshaft position sensor replaced, Evap system vent valve replaced, intake air boots replaced, general air filter/oil change done.

    -Two issues, first being that gas backs up into the fuel neck while filling the tank shutting off the the fuel nozzle.

    -The second being a clear difference in how the vehicle runs when under load and how it runs at idle. The vehicle seems to adjust to a different mixture when coming to a stop and can briefly run a bit rough at a low idle with all accessories off (650rpms-ish). Unprofessional analysis of fuel trims lead me to believe I had a vaccuum leak in the intake but I’ve smoke tested the intake where the evap system ties into the intake with zero luck locating any issues after replacing the bad (cracked) rubber intake connector boots.

    Fuel Trim data below taken at idle in park, 1500rpm in park, 2500rpm in park, and 2000rpm at 70mph on a flat stretch of highway. No codes. I’d assume the next step would be to check the exhaust system before the first O2 sensor on each bank, but I’d also considered that I potentially put the valve covers on poorly and they are drawing in extra air via the one-way PCV valve meaning it wouldn’t actually show up on a smoke test? Could a leak in the emissions system cause this as well, because I did have a P0455 code that I cleared after replacing the vent valve that has yet to come back after 4-500 miles? Any help on where to go next is appreciated!

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