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Discussion Starter · #1 · (Edited)
Hello guys, my car throwing code p0171 we change, Mass sensor, upstream and down stream O2 Sensor, we replace new start plug, intake manifold gasket, and PCV valve and checked all the hoses we even use smoke machine pressure to see if there any leak. Until now still throwing code P0171. What i notice is when its cold engine its hard to start at first try and second try its will start the engine easily, when i was driving every time the gear shift up or down the RPM dropping fast 3 to 0.5RPM. I reset the engine code and run idle for one hour no check engine light on, but if i鈥檓 driving maybe 15 to 30 minutes the engine light will on P0171, i have been driving every day 20 miles with no issue except for the RPM dropping fast when i was slowing down. So any idea need your advice this car making me broke 馃槗


****solved***the problem the fuel pump assembly not enough pressure its been 4 days now no check engine p0171
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I think, since you've done most probable things, and assuming they were done correctly it would be worth to TEST the fuel system, i.e. pump, injectors, fuel line, filters,...
 

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You replaced the intake gaskets - the code indicates "lean" condition which could be a bad upstream O2 sensor or vacuum leak. One suggestion would be to get a water spray bottle and spray all of the intake locations while monitoring the tachometer. Watch for RPM drops or engine hesitation. The smoke test is good for pressure leaks..water is better for intake leaks like cracked manifolds etc.

Get a scanner and data stream the O2 sensors to determine lean/rich condition and ensure the upstream sensor is actively cross counting while running.
 

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You replaced the intake gaskets - the code indicates "lean" condition which could be a bad upstream O2 sensor or vacuum leak. One suggestion would be to get a water spray bottle and spray all of the intake locations while monitoring the tachometer. Watch for RPM drops or engine hesitation. The smoke test is good for pressure leaks..water is better for intake leaks like cracked manifolds etc. Get a scanner and data stream the O2 sensors to determine lean/rich condition and ensure the upstream sensor is actively cross counting while running.
Do a full inspection of your exhaust system. Preferably on a lift while running. I have a 2015 Note SV and had the same exact issue. Apparently (and everyone reading this will agree) that Nissan exhaust systems are cheap and become porous. I replaced my entire exhaust ( well from the manifold on down) and lo and behold! All my emissions related codes are GONE! I found little pin hole along all the seams and welds鈥he system cost me $600 and some change from Rock. I saved a coupling hundred bucks by using a Walker 46 State compliant CAT, I鈥檓 in New Jersey so the Federal Cats are legal and now at 188,000 miles my blue Versa is my reliable weekend 鈥淗ome Depot/Lowes/ Get 鈥榚r Done鈥 Beater. Good luck , I鈥檒l keep reading to see how you make out.
 

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Its been 4 days driving the code p0171 is not showing up anymore and thank you all. I replace the fuel pump assembly my car start the engine on 1st try even its cold weather!
Great I鈥檓 happy to hear it. Hey maybe you can help me now鈥 replaced my Fuel Pump Unit about a year ago and I even bought the special tool from Amazon to remove the lock ring. The best $25 I ever spent. Saved me scrapped knuckles, time and headache. BUT!!! for the life of me I couldn鈥檛 get the new replacement green 鈥渙鈥 ring on, I just couldn鈥檛 compress it enough, so I reused the old ring, works fine, tight no leaks, no odor, good seal so I feel safe. How did you get the new o ring on or did you reuse the original like me? Thanks, MyBlue2015.
 

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Discussion Starter · #12 ·
Great I鈥檓 happy to hear it. Hey maybe you can help me now鈥 replaced my Fuel Pump Unit about a year ago and I even bought the special tool from Amazon to remove the lock ring. The best $25 I ever spent. Saved me scrapped knuckles, time and headache. BUT!!! for the life of me I couldn鈥檛 get the new replacement green 鈥渙鈥 ring on, I just couldn鈥檛 compress it enough, so I reused the old ring, works fine, tight no leaks, no odor, good seal so I feel safe. How did you get the new o ring on or did you reuse the original like me? Thanks, MyBlue2015.
They came with Green O Ring. I got spare one but i won鈥檛 promise to you if i can still find it at my garage i live in illinois. The weather here cold 馃ザ i will let you know soon.
 
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