Fault code PO171 system too lean

The check engine light on my daughters 2000 Sentra GXE 1.8 liter is on. The code is PO171 system too lean bank one. What could this be. I have replaced the top two O2 sensors. Thanks

Could be a simple clogged fuel filter.

If you regularly use fuel injector cleaners, the injectors are suffering. They may not be delivering the proper amount of fuel. Is the car running smoothly? Any misfiring?

When you start it cold it runs smooth for about 10 seconds, then it tries to die. While it's trying to die you can press the gas but the rpm doesn't change. After this it runs fine as long as the engine is warm. The gas mileage seems low, but she hasn't checked it.

hmmm, i would start with the fuel filter, then maybe the injectors. In the worst case scenario it may be the fuel pump or ECU.

i doubt its a physical problem with the fueling system. otherwise the car would run bad all the time. sounds to me like the ECU is getting the wrong information about how much fuel to supply on a cold start. doesnt sound like a bad ECU either but possibly a sensor or something. its definitely not getting fuel during that stumble, since throttle does nothing. i dont know for sure but i hope i narrowed it down some

check for any obvious air leaks from the air flow meter to the exhaust manifold. quite often i see air flow meters defective even though you dont have a p0100 code. air flow voltage will look normal, its the grams/sec that is the tell tell sign. ecm receives out of spec readings and will set the code. not sure if aftermarket scanners can read this but factory diag equipment can. may need to see your dealer. also check the start signal fuse, make sure its ok. good luck.

also,2000 and up sentra's do not have a replaceable fuel filter. only a screen on the fuel pump.

its not a fuse. dude get off the stealerships nutsack. this guy is obviously trying to find someone to help him without having to spend hundreds of dollars at a nissan shop. you havent proved that you know anything even though you work at a nissan dealer. its obvious to me that its not a vacuum leak because his gas pedal application does nothing. if its a vacuum leak, stepping on the gas will do somehting, even if all it does is make the car cough and sputter. how about trying to learn about cars at your job, then come back and offer some actually helpful advice, instead of telling people to waste money.

you obviously think you know more than you do slideshit. a start signal is fused and most newer cars have a rough time starting without it. do you even know what "lean" means? i'll explain it if you need me to. i suppose your diagnosis "a sensor or something" is much more helpful. i,ve seen this problem more times than you've spanked your monkey. maybe a snap-on or matco scanner can read grams/sec (do you need me to explain this too?) and he wont have to go to a dealer. i can see the "NO FEAR" stickers and your
wal-mart tool set from here.

you obviously think you know more than you do slideshit. a start signal is fused and most newer cars have a rough time starting without it. do you even know what "lean" means? i'll explain it if you need me to. i suppose your diagnosis "a sensor or something" is much more helpful. i,ve seen this problem more times than you've spanked your monkey. maybe a snap-on or matco scanner can read grams/sec (do you need me to explain this too?) and he wont have to go to a dealer. i can see the "NO FEAR" stickers and your
wal-mart tool set from here.

start signal.....hard to start without them??? so when the hell did he say he has hard time starting the car???

slideways was right that it couldn't be a leak otherwise the car idles rough all the time. and at least he point it out to look for the problems on the sensors, instead of u telling him to go to the dealer, which is the last thing ffwv needs.

....I think u just showed us how much u know about cars....same as those who works in the dealers.

WOW!
ok, fella's. LEAN means too much "air" in the "air/fuel" mixture. the most logical thing to look for is air leaks on the intake side, a cracked exhaust manifold, although kinda rare, can give you outta spec readings on your o2 sensors. if the air flow meter is malfunctioning and the ecm detects it, it will set a code according to logic programmed in the ecm. NOW PUT YOUR DUNCE CAPS BACK ON AND GO SIT IN THE CORNER OR I'LL TAKE YOUR RECESS AWAY!
i should have listened to my dad when he told me "NEVER ARGUE WITH IDOTS BECAUSE THEY WILL DRAG YOU DOWN TO THEIR LEVEL AND EVENTUALLY BEAT YOU WITH EXPERIENCE".
i probably have more time working on nissan's than you do wiping your own ass. checking fuses is mechanics 101, basic shit. if you were a real technician you'd know that. nobody is 100% right, 100% of the time. and trying to help someone without having your hands on the car is tough for anybody. so i would prefer someone with an education to help me. you may not think i know anything about nissan's that's because you're obviously not smart enough to even know what i'm talking about. so keep on sling'in parts, that what advance and autozone hope for.

WOW ok your that dumb? if air leaks out after the MAF reads it, you will run too RICH if anything. god wtf are you thinking. your shop pays you too much. this is what i mean about politics not filtering out dumb mechanics. nissan doc obviously does more ass kissing than wrench turning or else hed be working at walmart putting tires on 80 year old lady's buicks at his skill level

and he never said his car was hard to start. wtf does a start signal fuse have to do with a rough idle on cold start? JUST THINK FOR A SEC, PLEASE. IT HELPS!!!!!

and WTF are you suggesting???????? that telling him to go to a dealer for every problem is better than slingin parts at the problem?????

DUDE A CRACKED EXHAUST MANIFOLD WONT FUCK UP YOUR CAR ONLY ON COLD START!@!!!
if anything the 02 sensor will say its the SAME A/F MIXTURE even though some of the exhaust isnt reaching it. that wont make it read lean or rich...


but at least your on the right track its obviously a sensor problem, but it looks to me that it was more luck than anything that you got even that close. go back to your dad and whine that the mean people online are making you feel dumb. then go read "auto repair for dummies" and come back when you learn how to open your hood.

http://www.forumspile.com/Misc-Cluepon.jpg

nissandoc, id trust sideways more than you, u seem to be sayin dumb shit in every post that u make sayin to go the the dealership....sounds like some one isnt happy since they aint gettin no money for washin cars and changing oil....

1. sideways has been here longer than you
2. when teamed up with fugiot, they are the sentra 'gods' of this forum
3. ur just a dumb ass reading from procedures from the dealerships manuals
and finally 4. maybe we will give u some respect when you learn about what you are talkin about. get more3 posts and if u dont get flamed everytime anymore, then maybe just maybe you will just see how corrupted the stealerships really are y why Gm and Ford are losing money due to the dealerships and their problems...

WOW!
ok, fella's. LEAN means too much "air" in the "air/fuel" mixture. the most logical thing to look for is air leaks on the intake side, a cracked exhaust manifold, although kinda rare, can give you outta spec readings on your o2 sensors. if the air flow meter is malfunctioning and the ecm detects it, it will set a code according to logic programmed in the ecm. NOW PUT YOUR DUNCE CAPS BACK ON AND GO SIT IN THE CORNER OR I'LL TAKE YOUR RECESS AWAY!
i should have listened to my dad when he told me "NEVER ARGUE WITH IDOTS BECAUSE THEY WILL DRAG YOU DOWN TO THEIR LEVEL AND EVENTUALLY BEAT YOU WITH EXPERIENCE".
i probably have more time working on nissan's than you do wiping your own ass. checking fuses is mechanics 101, basic shit. if you were a real technician you'd know that. nobody is 100% right, 100% of the time. and trying to help someone without having your hands on the car is tough for anybody. so i would prefer someone with an education to help me. you may not think i know anything about nissan's that's because you're obviously not smart enough to even know what i'm talking about. so keep on sling'in parts, that what advance and autozone hope for.

dude, we all know what lean means.
the car idles rough ONLY when it's cold, then it just doesn't make sense that it's air leak.

and come on man.....I don't see what u saying, I think u trying to be funny though.
Yes checking fuses is a very basic thing, and everyone should know how.
My question is, did he say he has hard time starting the car???
NO HE DIDN"T!! Then what's the point to check for fuses?

basic shit huh?? so un.....Do u check fuses when u do oil change??
maybe it's a fuse that causes the oil turn black.....

Do u check fuses when u rotate tires??
maybe it's a fuse that causes the wear on the tires.....

Do u check fuses....man, nevermind.

and yeah, that's why I never like the dealers. They always assume that ppl doesn't know a shit. When u ask them what's wrong with the car, they'll guide u to the wrong direction, something like...."check for fuses" to solve the problem. So when u did, u couldn't find anything wrong, and u'll think u can't fix the problem then send ur car to the dealers.

and education.....dude, what the hell man??
u r working for a fucking dealer alright, what u think u r? a Ph. D? hahahahahaha.....
all the education means nothing without experiences.
yeah, u probably just gonna work for the dealer for the rest of ur life,
cause that's the ONLY place where u can make some money.

hey slideshit,my nismo sticker is peeling off of my hood and i think it may be causing some drag which is slowing my e.t's,should i get a new sticker or try some camber bolts like you....do those really increase hp like the magazine say's
oh,nice turd40 you punkass bitch

hey slideshit,my nismo sticker is peeling off of my hood and i think it may be causing some drag which is slowing my e.t's,should i get a new sticker or try some camber bolts like you....do those really increase hp like the magazine say's
oh,nice turd40 you punkass bitch

y don't u check for the fuse in ur head?
it definitely went bad, since ur brain ain't working

i think he needs some HKS blinker fluid for his eye-lids

naw naw naw...... he needs STAGE 3 BLINKER FLUID from hks..... stage one just wont hold up to his abuse

scratch that last one, that was the beer talkin'.
how about a role call guys? do you actually work on cars for a living? if so, how long? any certifications? what kind of experience do you really have? and why do you guys think that the more post's, stars, smiley faces or whatever makes you smarter. i,ll go first. so dont puss out.
2 yrs trade school, 7 yrs in the army working on anything and everything, 2 yrs at independent shop, 12 yrs at nissan dealer. ase certified master for 10 yrs, nissan certified master for 4 yrs. so lets hear from you slideways, nismowu, chiquae07. lets be honest now. and the fuse thing is getting old, i just have a habit of checking them before i spend 30 minutes on something only to find a blown fuse. and all the insults back and forth is fun and all, and kinda entertaining, but we arent getting anywhere. slideays please entertain yourself and ask one of your buddies at the dealership if an intake leak will cause it to run rich or lean. rich is fuel, lean is air. ffwv has already replaced the o2 sensors, so lets asume that we rule that out. what else will make it run lean?

plus, a leak in the intake would make it run lean under load, sure, but this guy is complaining about a rough idle, and only on cold start. back up and think about this for a sec. i dont care what certifications you have i care what you know.
btw ive worked in a shop for 1 year and im going to college for auto mechanics. not much but im only 23 so i cant have as much time in a shop as you. but i know now that im smarter than you so all this experience you have doesnt mean shit.

hey guys chill the fuck out...rather than beating each other over the head with how much experience y'all have, how about just giving the guy some ideas? if you haven't noticed, the guy hasn't really responded since this whole flamewar happened...chill out

nissandoc is right /do not listen to know it all young punk
im a nissan tech for 25 years . air flow meter will correct
problem with your car

i really dont have muc, but i asked my neighbor since he is always fixing his cars since he beats on them, but he said a rough idle in the cold could be a O2 sensor, leak in the intake, and i couldn't ell what else he said. i dont think it woulda helped if i told him it was a nissan since he is a ford/domestic guy, but cool about everything. if it is anyone that will help me with my vq35de swap, it would be him...

btw, its not genuine chevy lights unless it has LOF on it i think its LOF...

ok well if he is right ill admit it, since he stopped being an ass. but i dont ever remember him saying the MAF was bad...

other than that, any more argument and conjecture is pointless without results.

see im not just another knowitall punk. i didnt know how to even change my own oil 4 years ago. the amount that i know right now is more than many mechanics out there. im close to knowing enough to pass all my ASEs right now with only 2 quarters of school ever. at my shop, i constantly make over flatrate and sometimes more than some ASE mechanics there. dont doubt just because im younger than many people that my knowledge is lacking. and i also dont have the pride get in my way like some. i will admit if i get proven wrong here like in every instance. my only problem is that if someone is a dick i wont respect their knowledge since its not being applied in a constructive and positive manner. thats all.

scratch that last one, that was the beer talkin'.
how about a role call guys? do you actually work on cars for a living? if so, how long? any certifications? what kind of experience do you really have? and why do you guys think that the more post's, stars, smiley faces or whatever makes you smarter. i,ll go first. so dont puss out.
2 yrs trade school, 7 yrs in the army working on anything and everything, 2 yrs at independent shop, 12 yrs at nissan dealer. ase certified master for 10 yrs, nissan certified master for 4 yrs. so lets hear from you slideways, nismowu, chiquae07. lets be honest now. and the fuse thing is getting old, i just have a habit of checking them before i spend 30 minutes on something only to find a blown fuse. and all the insults back and forth is fun and all, and kinda entertaining, but we arent getting anywhere. slideays please entertain yourself and ask one of your buddies at the dealership if an intake leak will cause it to run rich or lean. rich is fuel, lean is air. ffwv has already replaced the o2 sensors, so lets asume that we rule that out. what else will make it run lean?

I'm still in kindergarten....feel better now?

anyway, is P0171 the only one code that he has?
cause that's just for the bank 1, which I think it's still O2 sensor.
Maybe he bought a defected one, or he got the wires mess up maybe?

A bad MAF sensor should cause both banks run too lean, not just one.

hey guys also check to see if you crossed up o/2 sensors connectors when you installed them / if so car will run very bad //

I will check the air flow meter, once I find out where it is and how to check it. It could be that one of the O2 sensors are hooked up wrong. I didn't do the work, they were done by the used car dealer that I bought it from. Thanks for the ideas!!

I will check the air flow meter, once I find out where it is and how to check it. It could be that one of the O2 sensors are hooked up wrong. I didn't do the work, they were done by the used car dealer that I bought it from. Thanks for the ideas!!

The sensor is between the intake box and the throttle body.
Very easy to find, it's connected with a 4 wire harness.
To do a basic check, start the engine, keep it running at idle speed
under warm-up condition.
Now the voltage of the green wire on the MAF sensor should be
approximately 1.3~1.7V
measure it again with engine running @ 2500 rpm
it should give u approximately 1.8~2.4V

anyone think mildly clogged cat? They dont work properly until at temp which is why the spec v has a precat to filter emissions during the cold period 0-15 minutes after starting..... this may explain why his AF mixture is screwy during startup but evens out when at temp........