Service Engine Soon: Code P0171
 

I'm back AGAIN!! I had a post about how the car wants stall when it starts after it sits overnight. Well I took it to Nissan and "everything checked out OK". Well 2 days later my check engine light came on and I had a code reader hooked up..the Code being P0171 Definition Fuel system lean bank 1 and bank 2
Probable cause: 1.Low Fuel pressure 2. Blocked Injectors 3. Large Vacuum Leak 4. MAF sensor fault
I looked up this error code before posting this and most people are saying it is a loose/not fully tight gas cap. I checked that over and over.
ANOTHER thing I noticed is that if I get on the gas aggressively, the car will studder at about 4 .5 RPM's. it is frustrating!! any ideas??

I also tried injector cleaner and making sure my air filters were seated ok.

any mods?

just the GT HAUS tail piece (cbe). Other than that nothing. Also, I put some injector cleaner in the gas to see if it was maybe some clogged injectors, no dice.

bad gas?

Well, I usually only put Shell's Ultra 93 in. I did notice it was pumping out very slow..maybe the last bit they had left. Not sure if that would have any effect.

Yah could be bad gas. Fill up using premium and see if it helps.

If it is not bad gas then it is likely a bad fuel pump. I've also had this code (on a different car) from a bad O2 sensor, but given that it is reporting it on both banks that doesn't seem to be the problem here. If you have any warranty left I would take it in and let them test the fuel pressure.

darn. i got that when i installed my HFC's..but once i added defoulers it was gone. likely some bad gas. try to siphon it out if you can (you can buy a pump relatively cheaply) and refill it with some good gas

any gas station can have water contaminated gas, put a fuel treatment in it and run it all through almost to the point of running out, refill (no additive this time) and see if that helped.

I will have to try this..any fuel treatment that you recommend? Is it ok to put it in with the Injector cleaner?

The injector cleaners are typically just a solvent like Toluene or Acetone. If you suspect water in the fuel system you can add a fuel stabilizer to get the water to mix with the fuel.

^ or zmax, burn it out

Funny u say that. I filled up with v power right after my oil change (castrol edge). The car. Felt sluggish as hell. Went back to quik trip gas and the car is ridiculously fast again. I only use vpower in my altima 3.5. And it does great. Not so with my Z.



If u live in dfw and never tried quik trip gas. Take the pepsi challenge. It will save you money too.

quik trip's and alot of those independent gas stations simply buy gas from whoever is cheaper at the time of ordering. it could very well be shell, chevron, or 76. how do i know? i have an acquaintance that runs a quik trip out here and he usually buys 76, but has told me hes gotten chevron, and shell many times. its a toss up really

Interesting..my grandfather was a mechanic for 35 years and told me he will only use Shell, so I kinda picked it up from him. But, last night I went out and reseated my air filters nice and tight..the CEL went away..i drove the car about 2 miles and it felt as if it was starting to get better...does it take a bit for the ECU to re-learn (if it even has to from something like that) or was there air in the engine somewhere causing the misfire/jumping of the car/engine?

if you're still having the problem this is what the FSM says
Intake air leaks
• A/F sensor 1
• Fuel injector
• Exhaust gas leaks
• Incorrect fuel pressure
• Lack of fuel
• Mass air flow sensor
• Incorrect PCV hose connection

also P0171 is the passenger side bank only not both banks, driver's side is p0174 the ecu takes two trips to throw the light and 3 trips with identical driving conditions to shut off the light by itself if the problem stops.

I've also had this code (on a different car) from a bad O2 sensor, but given that it is reporting it on both banks that doesn't seem to be the problem here.

i was wondering if you have got this problem fixed, i to am having that same problem i get on the gas aggressive it studders around 4-5k rpms and sounds like im red lining then. i noticed this after i was low on gas and filled up so i was thinking it is bad gas.

I had that code pop up about two months after installing my hfc's. I thought that it was due to the O2 sensors and the new hfc's but it turned out that the cause was due to a slipped hose clamp on the short ram that attached to the throttlebody. The ram slid out of the coupler and the engine was sucking in unmetered air. I replaced the flimsy coupler with a nice silicone hump coupler from Z1 Motorsports and hanen't seen that code since.

this only happens after the car sits for a long time? if so could be a leaky injector

Either bad vac leak somewhere near or in front of primary O2 (could also be exhaust leak just past it that causes a lean read), faulty MAF sensor, or bad O2.

09 370z won't start
 

I'm getting that code as well but my car won't start... died as I was driving it and that's the only code... would that code cause it to not start?

My P0171 and P0174 cause
 

My problem was caused by fake Denso Iridium FXE24HR11 spark plugs. The electrodes on all of these fake plugs melted to a gap of .075 to .080. I did buy new plugs from NGK, the Laser Iridium DF8H-11B plugs and this fixed my issue. I also replaced the front O2 sensors in the midst of troubleshooting my troubles. I had rough and misfiring issues with the fake plugs. I checked and tightened the entire intake tract and secured all vacuum hosing with fresh clamps to eliminate and vacuum leaks. The fake plugs were confirmed by the fact that the writing could easily be scraped off. The real Denso plugs do not let the lettering scrape off, the letters are under the glaze on the insulator. The fake plug issue is widespread on the web.

Hope this can help you ID some of your issues. Best of luck.