Fuel system running lean on bank 1 & 2
 

2010 370z Touring Roadster 38K

Banks 1 and 2 are running lean.
Codes P0171 and P0174 were thrown.
Probably causes were listed as:

Low Fuel pressure
Blocked injectors
Large vacuum leak
Mass air flow sensor fault


The car has the pickup of a ford pinto. Revving the engine in gear beyond 3,000 rpms results in no increase in power. I can't imagine both MAFs faulting at the same time. Air filters needed to be changed, so I did, disconnected the battery to let the computer reset, check engine light stayed off, but no change in performance. I can only imagine at this point that the fuel pump is covered in debris, or the injectors need to be pulled and cleaned.

The car is driven by my girlfriend who drives like an old lady in an Oldsmobile. I changed the battery in the car for her once and she never accelerates hard so the the computer never learned the range of throttle, and it ended up idling strange and sputtering forward when accelerating. I let it idle until warm, revved the engine into the 6k range several times, computer learned the range of throttle. problem solved. I am wondering if her grandma driving habits are the underlying cause of this leaned-out fuel system, and if the injectors are the likely cause. :facepalm:

We always use good gas, either Texaco or Shell.

Any input is appreciated. Thank you.

Check for vacuum leaks, possibly one of the rubber hoses has a crack in it. Also clean your MAFs and throttle bodies while you are at it.

Clean them? Like use some sea foam or something?

they make electronic cleaner spray...

http://contentinfo.autozone.com/znet...05110/image/3/

i dont really think this is true. after you reset the battery you dont have to drive it hard for the engine to relearn anything.


most likely it sounds like crappy gas, clogged injectors, or a fuel pump issue. my fuel pump died at 40k miles.

Okay, so I know it isn't the gas since we have gone through numerous tanks since that issue. Injectors can be cleaned correct? What about the fuel pump? If the mess screen is boogered up i'm assuming I can rinse it and reinstall. If not, what are my options for replacing it?

I would look at getting this, it beats trying to guess at all your fuel issues. This would atleast tell you what your pressures are like so you can either fix it or start looking somewhere else.

http://www.the370z.com/forced-induct...gauge-kit.html

Pulled the intake off and looked at the injectors on the car, they were all perfectly clean. The computer hasn't thrown the codes since I changed the air filters, but the power still flattens out after 3K RPMs and fuel mileage @65 MPH is ~22-24

Does this mean the fuel pump is going bad? When they go bad can they gradually lose pressure as the RPMs increases? From my experience with bad fuel pumps they tend to send spurts of fuel resulting in a jerky acceleration. If I put a pressure gauge on the line what psi should it be at?

Also when I pulled the intake off I visually inspected any vacuum tube I could see. All of the hoses were in mint condition, I have little reason to believe there is a vacuum leak.

I'm starting to wonder if I'm just imagining this power loss....

Idle fuel pressure is around 50-52PSI. Under WOT mine drops down to 36PSI however I would figure a stock car would sit around 40-45PSI.

How's your spark?

I had something similar a few months back, slow azz acceleration over 3000rpm (A Sentra probably would be faster than me). I also had huge afr difference between bank 1 and 2.

I had no codes though.....Dealer changed MAFs, checked brake fuse, throttle body relearn, redid valve covers because I also had oil inside valve cover on driver side and still same.

They ended up replacing ECM and everything is back to normal. (They said ECM was reading for automatic car for some reason)

How do I check?

Hold onto the plug wires :happydance:

Sounds like 7speed might be the one to talk to about this.

Leave the positive unhooked on the battery for 20 minutes then try. Sounds like limp mode. If not try the fuel pressure. If not that id point towards a crapped out injector or spark plug.